diff --git a/memoapp/README.md b/memoapp/README.md
index e267617..aeb1ef6 100644
--- a/memoapp/README.md
+++ b/memoapp/README.md
@@ -1,9 +1,9 @@
 ## Usage
 
-`git clone https://github.com/riq0h/memoapp.git`
-
-`cd memoapp`
-
-`bundle install`
-
-`ruby app.rb`
+```
+git clone https://github.com/riq0h/memoapp.git
+cd memoapp
+bundle install
+psql -U postgres -f memos.sql
+ruby app.rb
+```
diff --git a/memoapp/app.rb b/memoapp/app.rb
index 34977c7..f713f3e 100644
--- a/memoapp/app.rb
+++ b/memoapp/app.rb
@@ -2,29 +2,46 @@
 
 require 'sinatra'
 require 'sinatra/reloader'
-require 'json'
-require 'securerandom'
+require 'pg'
 require 'cgi'
 
-FILE_PATH = 'memos.json'
+configure do
+  set :conn, PG.connect(dbname: 'memo_app')
+end
 
 helpers do
   def h(text)
     CGI.escapeHTML(text.to_s)
   end
-end
 
-def load_memos
-  if !File.zero?(FILE_PATH)
-    JSON.parse(File.read(FILE_PATH))
-  else
-    {}
+  def db
+    settings.conn
   end
-end
 
-def save_memos(memos)
-  File.open(FILE_PATH, 'w') do |file|
-    file.write(JSON.generate(memos))
+  def find_memo(id)
+    db.exec_params('SELECT * FROM memos WHERE id = $1', [id]).first
+  end
+
+  def create_memo(title, content)
+    db.exec_params(
+      'INSERT INTO memos (title, content) VALUES ($1, $2) RETURNING id',
+      [title, content]
+    ).first['id']
+  end
+
+  def update_memo(id, title, content)
+    db.exec_params(
+      'UPDATE memos SET title = $1, content = $2 WHERE id = $3',
+      [title, content, id]
+    )
+  end
+
+  def delete_memo(id)
+    db.exec_params('DELETE FROM memos WHERE id = $1', [id])
+  end
+
+  def all_memos
+    db.exec('SELECT * FROM memos ORDER BY created_at DESC').to_a
   end
 end
 
@@ -33,7 +50,7 @@ get '/' do
 end
 
 get '/memos' do
-  @memos = load_memos
+  @memos = all_memos
   erb :index
 end
 
@@ -42,37 +59,29 @@ get '/memos/new' do
 end
 
 post '/memos' do
-  memos = load_memos
-  id = SecureRandom.uuid
-  memos[id] = { 'title' => params[:title], 'content' => params[:content] }
-  save_memos(memos)
-  redirect '/memos'
+  id = create_memo(params[:title], params[:content])
+  redirect "/memos/#{id}"
 end
 
 get '/memos/:id' do
-  @memo = load_memos[params[:id]]
+  @memo = find_memo(params[:id])
   halt 404, erb(:not_found) unless @memo
   erb :show
 end
 
 get '/memos/:id/edit' do
-  @memo = load_memos[params[:id]]
+  @memo = find_memo(params[:id])
   halt 404, erb(:not_found) unless @memo
   erb :edit
 end
 
 patch '/memos/:id' do
-  memos = load_memos
-  halt 404, erb(:not_found) unless memos[params[:id]]
-  memos[params[:id]] = { 'title' => params[:title], 'content' => params[:content] }
-  save_memos(memos)
+  update_memo(params[:id], params[:title], params[:content])
   redirect "/memos/#{params[:id]}"
 end
 
 delete '/memos/:id' do
-  memos = load_memos
-  halt 404, erb(:not_found) unless memos.delete(params[:id])
-  save_memos(memos)
+  delete_memo(params[:id])
   redirect '/memos'
 end
 
diff --git a/memoapp/memos.sql b/memoapp/memos.sql
new file mode 100644
index 0000000..f712772
--- /dev/null
+++ b/memoapp/memos.sql
@@ -0,0 +1,9 @@
+CREATE DATABASE memo_app;
+DROP TABLE IF EXISTS memos;
+\c memo_app
+CREATE TABLE memos (
+  id UUID PRIMARY KEY DEFAULT gen_random_uuid(),
+  title VARCHAR(255) NOT NULL,
+  content TEXT NOT NULL,
+  created_at TIMESTAMP DEFAULT CURRENT_TIMESTAMP
+);
diff --git a/memoapp/public/styles.css b/memoapp/public/styles.css
index 659d156..dcd1c7c 100644
--- a/memoapp/public/styles.css
+++ b/memoapp/public/styles.css
@@ -1,3 +1,10 @@
+:root {
+  --save-color: #007bff;
+  --edit-color: #28a745;
+  --delete-color: #dc3545;
+  --back-color: #6c757d;
+}
+
 body {
   font-family: Arial, sans-serif;
   background-color: #f0f0f0;
@@ -35,7 +42,7 @@ nav {
 nav a {
   margin: 0 10px;
   text-decoration: none;
-  color: #007bff;
+  color: var(--save-color);
 }
 
 nav a:hover {
@@ -59,44 +66,42 @@ form textarea {
   border-radius: 4px;
 }
 
-form button {
+.button {
   padding: 10px;
   color: #fff;
   border: none;
   border-radius: 4px;
   cursor: pointer;
+  text-decoration: none;
+  text-align: center;
+  display: inline-block;
+  width: 100%;
 }
 
-form button.save {
-  background-color: #007bff;
+.button:hover {
+  opacity: 0.9;
 }
 
-form button.save:hover {
-  background-color: #0056b3;
+.button.save {
+  background-color: var(--save-color);
 }
 
-form button.delete {
-  background-color: #dc3545;
+.button.delete {
+  background-color: var(--delete-color);
+  padding: 12px;
+  font-size: 90%;
 }
 
-form button.delete:hover {
-  background-color: #c82333;
+.button.edit {
+  background-color: var(--edit-color);
 }
 
-form button.edit {
-  background-color: #28a745;
-}
-
-form button.edit:hover {
-  background-color: #218838;
-}
-
-form button.back {
-  background-color: #6c757d;
-}
-
-form button.back:hover {
-  background-color: #5a6268;
+.button.back {
+  background-color: var(--back-color);
+  margin-top: 10px;
+  display: block;
+  margin: 10px auto 0;
+  box-sizing: border-box;
 }
 
 .memo-list {
@@ -110,7 +115,7 @@ form button.back:hover {
 
 .memo-list a {
   text-decoration: none;
-  color: #007bff;
+  color: var(--save-color);
 }
 
 .memo-list a:hover {
@@ -123,27 +128,18 @@ form button.back:hover {
   margin-bottom: 10px;
 }
 
-.memo-actions form {
-  display: inline;
+.memo-actions form,
+.memo-actions a {
+  flex: 1;
+  margin: 0 5px;
 }
 
-.memo-actions button {
-  padding: 10px;
-  color: #fff;
-  border: none;
-  border-radius: 4px;
-  cursor: pointer;
+.memo-actions form:first-child,
+.memo-actions a:first-child {
+  margin-left: 0;
 }
 
-.memo-actions .edit {
-  background-color: #28a745;
+.memo-actions form:last-child,
+.memo-actions a:last-child {
+  margin-right: 0;
 }
-
-.memo-actions .edit:hover {
-  background-color: #218838;
-}
-
-.memo-actions .back {
-  background-color: #6c757d;
-}
-
diff --git a/memoapp/views/edit.erb b/memoapp/views/edit.erb
index 5f940d7..e335ad3 100644
--- a/memoapp/views/edit.erb
+++ b/memoapp/views/edit.erb
@@ -1,8 +1,8 @@
-<form action="/memos/<%= params[:id] %>" method="post">
+<form action="/memos/<%= @memo['id'] %>" method="post">
 <input type="hidden" name="_method" value="patch">
 <label for="title">タイトル</label>
 <input type="text" name="title" id="title" value="<%= h(@memo['title']) %>">
 <label for="content">内容</label>
 <textarea name="content" id="content"><%= h(@memo['content']) %></textarea>
-<button type="submit" class="edit">変更</button>
+<button type="submit" class="button save">保存</button>
 </form>
diff --git a/memoapp/views/index.erb b/memoapp/views/index.erb
index ee2eee6..c24bd92 100644
--- a/memoapp/views/index.erb
+++ b/memoapp/views/index.erb
@@ -1,5 +1,5 @@
 <ul class="memo-list">
-<% @memos.each do |id, memo| %>
-  <li><a href="/memos/<%= id %>"><%= h(memo["title"]) %></a></li>
+<% @memos.each do |memo| %>
+  <li><a href="/memos/<%= memo['id'] %>"><%= h(memo['title']) %></a></li>
 <% end %>
 </ul>
diff --git a/memoapp/views/new.erb b/memoapp/views/new.erb
index 125b083..749a689 100644
--- a/memoapp/views/new.erb
+++ b/memoapp/views/new.erb
@@ -3,5 +3,5 @@
 <input type="text" name="title" id="title">
 <label for="content">内容</label>
 <textarea name="content" id="content"></textarea>
-<button type="submit" class="save">保存</button>
+<button type="submit" class="button save">保存</button>
 </form>
diff --git a/memoapp/views/not_found.erb b/memoapp/views/not_found.erb
index 5bb9ea4..4a1a28d 100644
--- a/memoapp/views/not_found.erb
+++ b/memoapp/views/not_found.erb
@@ -1,3 +1,3 @@
-<h1>404 Not Found</h1>
+<h2>404 Not Found</h2>
 <p>お探しのページは見つかりませんでした。</p>
 <a href="/">トップページに戻る</a>
diff --git a/memoapp/views/show.erb b/memoapp/views/show.erb
index e3bf232..be297f4 100644
--- a/memoapp/views/show.erb
+++ b/memoapp/views/show.erb
@@ -1,14 +1,10 @@
 <h2><%= h(@memo['title']) %></h2>
 <p><%= h(@memo['content']) %></p>
 <div class="memo-actions">
-  <form action="/memos/<%= params[:id] %>/edit" method="get">
-    <button type="submit" class="edit">変更</button>
-  </form>
-  <form action="/memos/<%= params[:id] %>" method="post">
+  <a href="/memos/<%= @memo['id'] %>/edit" class="button edit">編集</a>
+  <form action="/memos/<%= @memo['id'] %>" method="post">
     <input type="hidden" name="_method" value="delete">
-    <button type="submit" class="delete">削除</button>
+    <button type="submit" class="button delete">削除</button>
   </form>
 </div>
-<form action="/memos" method="get">
-  <button type="submit" class="back">戻る</button>
-</form>
+<a href="/memos" class="button back">戻る</a>