diff --git a/05.wc/wc.rb b/05.wc/wc.rb
new file mode 100644
index 0000000000..c642c34e80
--- /dev/null
+++ b/05.wc/wc.rb
@@ -0,0 +1,70 @@
+# ! /usr/bin/env ruby
+# frozen_string_literal: true
+
+require 'optparse'
+
+STDIN_PATTERN = /^-$/
+TOTAL = '合計'
+
+def main
+  options = parse_options(ARGV)
+  rows = build_rows(options)
+  show_rows(rows)
+end
+
+def build_rows(options)
+  rows = []
+  ARGF.each(nil) do |input_text|
+    counts = {}
+
+    counts[:filename] = ARGF.filename
+    counts[:line] = input_text.lines.count if options[:l]
+    counts[:word] = input_text.split(/\s+/).size if options[:w]
+    counts[:byte] = input_text.size if options[:c]
+    rows << counts
+  end
+  rows << calculate_total_rows(rows) if rows.size > 1
+  rows
+end
+
+def calculate_total_rows(rows)
+  total = rows.inject({}) do |result, counts|
+    result.merge(counts) do |key, current_val, adding_value|
+      current_val + adding_value unless key == :filename
+    end
+  end
+  total[:filename] = TOTAL
+  total
+end
+
+def show_rows(rows)
+  max_widths = calculate_max_widths(rows)
+  rows.each do |counts|
+    columns = counts.to_h do |name, value|
+      text = name == :filename ? value.sub(STDIN_PATTERN, '') : value.to_s.rjust(max_widths[name])
+      [name, text]
+    end
+    puts columns.values_at(:line, :word, :byte, :filename).join(' ')
+  end
+end
+
+def calculate_max_widths(rows)
+  %i[line word byte].to_h do |name|
+    max_width = rows.map { |counts| counts[name].to_s.length }.max
+    [name, max_width]
+  end
+end
+
+def parse_options(argv)
+  options = {}
+  OptionParser.new do |opt|
+    opt.on('-l') { |v| options[:l] = v }
+    opt.on('-w') { |v| options[:w] = v }
+    opt.on('-c') { |v| options[:c] = v }
+    opt.parse!(argv)
+  end
+
+  options.empty? ? { l: true, w: true, c: true } : options
+end
+
+main