diff --git a/functions/customizer.php b/functions/customizer.php
index 6489ca4..bed247f 100644
--- a/functions/customizer.php
+++ b/functions/customizer.php
@@ -95,6 +95,18 @@ function add_theme_customizer($wp_customize) {
     ),
     'priority' => 10
   ));
+  $wp_customize->add_setting('preview_add_thumbnail', array(
+    'default' => false,
+    'type' => 'option'
+  ));
+  $wp_customize->add_control('preview_add_thumbnail', array(
+    'label' => 'アイキャッチをページ上部に表示',
+    'description' => '',
+    'section' => 'preview_section',
+    'settings' => 'preview_add_thumbnail',
+    'type' => 'checkbox',
+    'priority' => 11
+  ));
 
   // Custom Admin
   $wp_customize->add_section('admin_section', array(
diff --git a/page.php b/page.php
index 8f584cf..5684d3d 100644
--- a/page.php
+++ b/page.php
@@ -14,6 +14,14 @@
       <?php if (have_posts()): ?>
         <article class="article">
           <?php while (have_posts()): the_post(); ?>
+            <?php
+              $preview_add_thumbnail = get_option('preview_add_thumbnail');
+              if (has_post_thumbnail() && $preview_add_thumbnail):
+            ?>
+              <div class="article-thumbnail-wrap">
+                <?php the_post_thumbnail('large'); ?>
+              </div>
+            <?php endif; ?>
             <header class="article-header">
               <?php get_template_part('components/app-title'); ?>
             </header>
diff --git a/single.php b/single.php
index 305ab01..8100736 100644
--- a/single.php
+++ b/single.php
@@ -14,6 +14,14 @@
       <?php if (have_posts()): ?>
         <article class="article">
           <?php while (have_posts()): the_post(); ?>
+            <?php
+              $preview_add_thumbnail = get_option('preview_add_thumbnail');
+              if (has_post_thumbnail() && $preview_add_thumbnail):
+            ?>
+              <div class="article-thumbnail-wrap">
+                <?php the_post_thumbnail('large'); ?>
+              </div>
+            <?php endif; ?>
             <header class="article-header">
               <?php get_template_part('components/app-title'); ?>
               <p class="article-date">
diff --git a/style.css b/style.css
index 3e22721..fc03194 100644
--- a/style.css
+++ b/style.css
@@ -46,10 +46,9 @@ a:hover {
   text-decoration: none;
 }
 
-img,
-iframe,
-textarea {
+img {
   max-width: 100%;
+  height: auto;
 }
 
 h1,