diff --git a/apps/web/src/features/auth/model/useWithdraw.ts b/apps/web/src/features/auth/model/useWithdraw.ts
index c42ac3c4..3af439d6 100644
--- a/apps/web/src/features/auth/model/useWithdraw.ts
+++ b/apps/web/src/features/auth/model/useWithdraw.ts
@@ -6,6 +6,7 @@ import { useToast } from '@/shared/ui';
 import { clearAllUserStorage } from '@/shared/utils';
 import { authQueries } from './authQueries';
 import { useBridge } from '@/shared/lib/bridge';
+import { handleApiError } from '@/shared/api';
 
 export const useWithdraw = () => {
   const router = useRouter();
@@ -29,12 +30,13 @@ export const useWithdraw = () => {
       toast.success('회원탈퇴가 완료되었어요');
       router.replace('/login');
     },
-    onError: (error: Error) => {
-      const message =
-        error?.message && error.message !== 'Failed to fetch'
-          ? error.message
-          : '회원 탈퇴에 실패했어요. 다시 시도해주세요.';
-      toast.attention(message);
+    onError: (error) => {
+      handleApiError(error, {
+        toast,
+        fallback: '회원 탈퇴에 실패했어요. 다시 시도해 주세요.',
+        context: 'auth.withdraw',
+        preferServerMessage: true,
+      });
     },
   });
 
diff --git a/apps/web/src/features/expense/ui/ExpenseEditBottomSheet.tsx b/apps/web/src/features/expense/ui/ExpenseEditBottomSheet.tsx
index b9b7fb36..a3e8300b 100644
--- a/apps/web/src/features/expense/ui/ExpenseEditBottomSheet.tsx
+++ b/apps/web/src/features/expense/ui/ExpenseEditBottomSheet.tsx
@@ -24,6 +24,7 @@ import {
 } from '@/entities/expense';
 import { expenseReportQueries } from '@/entities/expenseReport';
 import { expenseEditNavigation } from '@/features/expense/lib/expenseEditNavigation';
+import { handleApiError } from '@/shared/api';
 
 export interface ExpenseEditBottomSheetProps {
   isOpen: boolean;
@@ -88,8 +89,11 @@ export const ExpenseEditBottomSheet = ({
       onClose();
     },
     onError: (error) => {
-      console.error('지출 수정 실패:', error);
-      toast.attention('수정에 실패했어요. 다시 시도해 주세요.');
+      handleApiError(error, {
+        toast,
+        fallback: '수정에 실패했어요. 다시 시도해 주세요.',
+        context: 'expense.update',
+      });
     },
   });
   // 지출 삭제 mutation
@@ -105,8 +109,11 @@ export const ExpenseEditBottomSheet = ({
       onClose();
     },
     onError: (error) => {
-      console.error('지출 삭제 실패:', error);
-      toast.attention('삭제에 실패했어요. 다시 시도해 주세요.');
+      handleApiError(error, {
+        toast,
+        fallback: '삭제에 실패했어요. 다시 시도해 주세요.',
+        context: 'expense.delete',
+      });
     },
   });
 
diff --git a/apps/web/src/features/expense/ui/steps/AddCategoryStep/AddCategoryStep.tsx b/apps/web/src/features/expense/ui/steps/AddCategoryStep/AddCategoryStep.tsx
index fcecbef6..fed6c6a7 100644
--- a/apps/web/src/features/expense/ui/steps/AddCategoryStep/AddCategoryStep.tsx
+++ b/apps/web/src/features/expense/ui/steps/AddCategoryStep/AddCategoryStep.tsx
@@ -25,6 +25,7 @@ import { useExpenseFormStore } from '@/widgets/expenseRecordFunnel/model/store';
 import { useQuery, useMutation, useQueryClient } from '@tanstack/react-query';
 import { categoryQueries } from '@/features/expense/model/categoryQueries';
 import { CategoryDetailsDTO } from '@/features/expense/model/types';
+import { handleApiError } from '@/shared/api';
 
 const VALID_NAME_REGEX = /^[가-힣ㄱ-ㅎㅏ-ㅣa-zA-Z0-9]*$/;
 
@@ -60,6 +61,13 @@ export const AddCategoryStep = ({ onBack }: AddCategoryStepProps) => {
       useExpenseFormStore.setState({ shouldOpenCategorySheet: false });
       onBack();
     },
+    onError: (error) => {
+      handleApiError(error, {
+        toast,
+        fallback: '카테고리 추가에 실패했어요. 다시 시도해 주세요.',
+        context: 'category.create',
+      });
+    },
   });
 
   const [categoryName, setCategoryName] = useState('');
diff --git a/apps/web/src/features/inquiry/model/useInquiryForm.ts b/apps/web/src/features/inquiry/model/useInquiryForm.ts
index 56d7d170..f5924620 100644
--- a/apps/web/src/features/inquiry/model/useInquiryForm.ts
+++ b/apps/web/src/features/inquiry/model/useInquiryForm.ts
@@ -5,6 +5,7 @@ import { useModal } from '@/shared/hooks';
 import { isValidEmail, hasEmailError } from '@/shared/lib/validation';
 import { inquiryQueries } from './inquiryQueries';
 import { useToast } from '@/shared/ui';
+import { handleApiError } from '@/shared/api';
 
 /**
  * 문의 폼 상태 및 동작을 관리하는 커스텀 훅
@@ -25,8 +26,12 @@ export const useInquiryForm = () => {
       toast.success('등록 완료, 곧 답변드릴게요!');
       router.back();
     },
-    onError: () => {
-      toast.attention('문의 등록에 실패했어요. 다시 시도해주세요.');
+    onError: (error) => {
+      handleApiError(error, {
+        toast,
+        fallback: '문의 등록에 실패했어요. 다시 시도해 주세요.',
+        context: 'inquiry.send',
+      });
     },
   });
 
diff --git a/apps/web/src/features/review/model/useSpendingReview.ts b/apps/web/src/features/review/model/useSpendingReview.ts
index cd972ad1..53da2539 100644
--- a/apps/web/src/features/review/model/useSpendingReview.ts
+++ b/apps/web/src/features/review/model/useSpendingReview.ts
@@ -11,6 +11,7 @@ import { ROUTES } from '@/shared/constants/routes';
 import { useRetrospectExpenses } from './useRetrospectExpenses';
 import { patchRemind } from '../api/patchRemind';
 import { useReviewCarousel, type UseReviewCarouselReturn } from './useReviewCarousel';
+import { handleApiError } from '@/shared/api';
 
 type UseSpendingReviewReturn = Pick<
   UseReviewCarouselReturn,
@@ -63,6 +64,13 @@ export const useSpendingReview = ({ date }: UseSpendingReviewParams): UseSpendin
       toast.success('만족도 기록이 잘 저장되었어요!');
       router.push(ROUTES.HOME);
     },
+    onError: (error) => {
+      handleApiError(error, {
+        toast,
+        fallback: '저장에 실패했어요. 다시 시도해 주세요.',
+        context: 'review.saveRemind',
+      });
+    },
   });
 
   const buildRemindBody = () =>
diff --git a/apps/web/src/shared/api/client.ts b/apps/web/src/shared/api/client.ts
index 77010606..9d1c35be 100644
--- a/apps/web/src/shared/api/client.ts
+++ b/apps/web/src/shared/api/client.ts
@@ -81,10 +81,12 @@ export const apiClient = ky.create({
         }
         if (error.response) {
           try {
-            const body = await error.response.text();
-            error.message = `${error.message}: ${body}`;
+            const body = (await error.response.clone().json()) as { message?: string };
+            if (body?.message) {
+              error.message = body.message;
+            }
           } catch {
-            // 응답 본문 읽기 실패 시 무시
+            // JSON 파싱 실패 시 원본 message 유지
           }
         }
         return error;
diff --git a/apps/web/src/shared/api/handleApiError.ts b/apps/web/src/shared/api/handleApiError.ts
new file mode 100644
index 00000000..cf092095
--- /dev/null
+++ b/apps/web/src/shared/api/handleApiError.ts
@@ -0,0 +1,43 @@
+import { HTTPError } from 'ky';
+
+export interface ToastApi {
+  attention: (message: string) => void;
+}
+
+export interface HandleApiErrorOptions {
+  /** 사용자에게 노출할 기본 실패 문구 (서버 메시지가 없거나 사용 불가일 때 사용) */
+  fallback: string;
+  /** 토스트 인스턴스 (useToast() 결과) */
+  toast: ToastApi;
+  /** 디버깅용 컨텍스트 (예: 'expense.update') */
+  context?: string;
+  /**
+   * true이면 HTTP 응답에서 받은 서버 메시지(error.message)를 우선 노출.
+   * 네트워크 오류 등 응답이 없는 경우엔 fallback을 사용.
+   * 기본 false.
+   */
+  preferServerMessage?: boolean;
+}
+
+const SILENT_STATUS = new Set([401, 403]);
+
+/**
+ * mutation/쿼리의 onError에서 사용할 공통 핸들러.
+ * - 401/403은 client.ts에서 reissue/리다이렉트 처리하므로 토스트를 띄우지 않음
+ * - 기본은 fallback 문구 노출. preferServerMessage=true이면 HTTPError의 서버 메시지 우선
+ * - console.error를 일관 포맷으로 출력
+ */
+export const handleApiError = (error: unknown, options: HandleApiErrorOptions) => {
+  const { fallback, toast, context, preferServerMessage = false } = options;
+
+  if (error instanceof HTTPError && SILENT_STATUS.has(error.response.status)) {
+    return;
+  }
+
+  console.error(`[API Error]${context ? ` ${context}` : ''}:`, error);
+
+  const serverMessage =
+    preferServerMessage && error instanceof HTTPError && error.message ? error.message : null;
+
+  toast.attention(serverMessage ?? fallback);
+};
diff --git a/apps/web/src/shared/api/index.ts b/apps/web/src/shared/api/index.ts
index 4516ae26..fe5b1bd0 100644
--- a/apps/web/src/shared/api/index.ts
+++ b/apps/web/src/shared/api/index.ts
@@ -2,4 +2,6 @@ export { apiClient, authenticatedApiClient } from './client';
 export { api, authApi } from './methods';
 export { API_BASE_URL, API_TIMEOUT, API_RETRY_LIMIT } from './constants';
 export { ENDPOINT } from './endpoint';
+export { handleApiError } from './handleApiError';
 export type { ApiResponse } from './types';
+export type { HandleApiErrorOptions, ToastApi } from './handleApiError';
diff --git a/apps/web/src/widgets/addCategory/ui/AddCategory.tsx b/apps/web/src/widgets/addCategory/ui/AddCategory.tsx
index d970c396..dabe392b 100644
--- a/apps/web/src/widgets/addCategory/ui/AddCategory.tsx
+++ b/apps/web/src/widgets/addCategory/ui/AddCategory.tsx
@@ -25,6 +25,7 @@ import { useExpenseFormStore } from '@/widgets/expenseRecordFunnel/model/store';
 import { useQuery, useMutation, useQueryClient } from '@tanstack/react-query';
 import { categoryQueries } from '@/features/expense/model/categoryQueries';
 import { CategoryDetailsDTO } from '@/features/expense/model/types';
+import { handleApiError } from '@/shared/api';
 
 const VALID_NAME_REGEX = /^[가-힣ㄱ-ㅎㅏ-ㅣa-zA-Z0-9]*$/;
 
@@ -68,6 +69,13 @@ export const AddCategory = () => {
       }
       toast.success('카테고리가 추가되었어요!');
     },
+    onError: (error) => {
+      handleApiError(error, {
+        toast,
+        fallback: '카테고리 추가에 실패했어요. 다시 시도해 주세요.',
+        context: 'category.create',
+      });
+    },
   });
 
   const { mutate: updateCategory, isPending: isUpdatePending } = useMutation({
@@ -78,6 +86,13 @@ export const AddCategory = () => {
       toast.success('수정한 내용이 저장되었어요!');
       router.back();
     },
+    onError: (error) => {
+      handleApiError(error, {
+        toast,
+        fallback: '카테고리 수정에 실패했어요. 다시 시도해 주세요.',
+        context: 'category.update',
+      });
+    },
   });
 
   const isPending = isCreatePending || isUpdatePending;
diff --git a/apps/web/src/widgets/expenseRecordFunnel/ui/ExpenseRecordFunnel.tsx b/apps/web/src/widgets/expenseRecordFunnel/ui/ExpenseRecordFunnel.tsx
index dddff983..b256ecd0 100644
--- a/apps/web/src/widgets/expenseRecordFunnel/ui/ExpenseRecordFunnel.tsx
+++ b/apps/web/src/widgets/expenseRecordFunnel/ui/ExpenseRecordFunnel.tsx
@@ -28,6 +28,7 @@ import { useMutation, useQueryClient } from '@tanstack/react-query';
 import { expenseReportQueries } from '@/entities/expenseReport';
 import { expenseQueries as entityExpenseQueries } from '@/entities/expense';
 import { ROUTES } from '@/shared/constants';
+import { handleApiError } from '@/shared/api';
 
 const STEP_NUMBER = {
   금액날짜입력: 1,
@@ -86,7 +87,16 @@ export const ExpenseRecordFunnel = () => {
       history.push('만족도입력', { usageHistory, categoryId });
     };
 
-  const { mutate: submitExpense, isPending } = useMutation(expenseQueries.recordMutation());
+  const { mutate: submitExpense, isPending } = useMutation({
+    ...expenseQueries.recordMutation(),
+    onError: (error) => {
+      handleApiError(error, {
+        toast,
+        fallback: '저장에 실패했어요. 다시 시도해 주세요.',
+        context: 'expense.create',
+      });
+    },
+  });
 
   const handleSubmit = (emotionType: EmotionType) => {
     if (isPending) return;
@@ -106,9 +116,6 @@ export const ExpenseRecordFunnel = () => {
           toast.success('소비 기록이 저장되었어요.');
           router.push(ROUTES.HOME);
         },
-        onError: () => {
-          toast.attention('저장에 실패했어요. 다시 시도해 주세요.');
-        },
       }
     );
   };
diff --git a/apps/web/src/widgets/notifications/ui/Notifications.tsx b/apps/web/src/widgets/notifications/ui/Notifications.tsx
index 5a9e4a41..ba13ed2b 100644
--- a/apps/web/src/widgets/notifications/ui/Notifications.tsx
+++ b/apps/web/src/widgets/notifications/ui/Notifications.tsx
@@ -18,6 +18,10 @@ export const Notifications = ({ onBackClick }: NotificationsProps) => {
     onSuccess: () => {
       queryClient.invalidateQueries({ queryKey: notificationQueries.all });
     },
+    onError: (error) => {
+      // 읽음 처리는 백그라운드성 동작이라 토스트 없이 로그만 남긴다
+      console.error('[API Error] notification.readAll:', error);
+    },
   });
 
   const handleBackClick = () => {