diff --git a/lib/css/chat-layout-pc.css b/lib/css/chat-layout-pc.css
index e2ab8d59..ca960477 100644
--- a/lib/css/chat-layout-pc.css
+++ b/lib/css/chat-layout-pc.css
@@ -936,12 +936,23 @@ body {
   left: 5em;
   right: auto;
   bottom: 8em;
+  max-height: 40vh;
+  min-height: 12rem;
+  min-width: 42vw;
+
+  > .comm-area {
+    height: calc(100% - (0.5rem * 2) - (3rem + ((2rem * 2) + 0.1rem)));
+    margin-top: 0.5rem;
+    margin-bottom: 0.5rem;
+
+    textarea {
+      height: 100%;
+      overflow-y: auto;
+    }
+  }
 }
 #rewrite-form textarea {
-  width: 40vw;
-  max-width: 90vw;
-  max-height: 80vh;
-  margin-top: .1rem;
+  margin: 0;
 }
 #rewrite-name-form {
   top: auto;
diff --git a/lib/html/room.html b/lib/html/room.html
index 6f7d6719..64af440e 100644
--- a/lib/html/room.html
+++ b/lib/html/room.html
@@ -246,7 +246,7 @@ <h2>発言名変更</h2>
   <div class="float-box" id="rewrite-form">
     <h2>発言編集</h2>
     <div class="comm-area">
-      <textarea class="autosize" id="rewrite-comm" data-comm-pre=""></textarea>
+      <textarea id="rewrite-comm" data-comm-pre=""></textarea>
       <button onclick="formSubmit('rewrite-comm');boxClose('rewrite-form');">送信</button>
     </div>
     
diff --git a/lib/js/ui.js b/lib/js/ui.js
index 7d9d8dc6..985c7365 100644
--- a/lib/js/ui.js
+++ b/lib/js/ui.js
@@ -449,8 +449,33 @@ function rewriteOpen(num){
     .replace(/&lt;/g, '<')
     .replace(/&gt;/g, '>')
   obj.value = setValue;
-  autosizeUpdate(obj);
   obj.focus();
+
+  {
+    const sourceMessageNode = document.getElementById(`line-${num}-comm`);
+
+    if (sourceMessageNode != null) {
+      const rewriteForm = document.getElementById('rewrite-form');
+      const tabGroupNode = sourceMessageNode.closest('.tab-group');
+      const isMain = tabGroupNode.classList.contains('main');
+
+      const rect = sourceMessageNode.getBoundingClientRect();
+
+      const x = isMain ? rect.left : rect.right - rewriteForm.getBoundingClientRect().width;
+      const y = Math.min(rect.bottom + 15, tabGroupNode.getBoundingClientRect().bottom);
+
+      const m = rewriteForm.style.inset.match(/^[\d.]+px\s+(\S+)\s+(\S+)\s+[\d.]+px$/);
+
+      if (m != null) {
+        rewriteForm.style.inset = `${y}px ${m[1]} ${m[2]} ${x}px`;
+      } else {
+        rewriteForm.style.left = `${x}px`;
+        rewriteForm.style.right = 'auto';
+        rewriteForm.style.top = `${y}px`;
+        rewriteForm.style.bottom = 'auto';
+      }
+    }
+  }
 }
 function rewriteNameOpen(num,name){
   boxOpen('rewrite-name-form');