diff --git a/_layouts/default.html b/_layouts/default.html
index 4013bcb..ae5c367 100644
--- a/_layouts/default.html
+++ b/_layouts/default.html
@@ -32,7 +32,7 @@ layout: compress
 
   <body>
     <!-- モバイルメニュー -->
-    <amp-sidebar id="sidebar" side="right" layout="nodisplay">
+    <amp-sidebar id="sidebar" side="left" layout="nodisplay">
       <button on="tap:sidebar.close">
         <amp-img
           height = "2em"
diff --git a/_sass/_header.scss b/_sass/_header.scss
index 5cc780d..5d15c38 100644
--- a/_sass/_header.scss
+++ b/_sass/_header.scss
@@ -3,12 +3,18 @@ header {
   background: $header-background;
   box-sizing: border-box;
   font-weight: bold;
-  padding: 1em;
+  height: 3em;
+  line-height: 3em;
+
+  @include media-desktop {
+    padding: 0 1em;
+  }
 
   @include media-mobile {
     box-shadow: $header-mobile-box-shadow;
     position: fixed;
     width: 100%;
+    text-align: center;
     z-index: 9999;
   }
 
@@ -24,8 +30,8 @@ header {
     }
 
     > amp-img {
-      float: left;
-      margin: $header-img-vertical-adjustment 1em 0 0;
+      margin-top: $header-img-vertical-adjustment;
+      vertical-align: middle;
     }
   }
 
@@ -33,8 +39,11 @@ header {
     background: transparent;
     border: none;
     float: right;
+    left: 1em;
     object-fit: contain;
     padding: 0 1em;
+    position: absolute;
+    top: 1em;
 
     @include media-desktop {
       display: none;
