diff --git a/development_status.md b/development_status.md
index 1f2fb65..a5ecf4f 100644
--- a/development_status.md
+++ b/development_status.md
@@ -1,6 +1,6 @@
 # CertRemind 開発進捗
 
-最終更新: 2026-05-25
+最終更新: 2026-05-27
 
 ## 現在の実装状況
 
@@ -244,7 +244,7 @@ pnpm monitor:worker
   - 確認ダイアログ付き履歴削除
 - 通知方法管理画面
   - Webhook 登録
-  - Webhook 編集
+  - モーダルでの Webhook 編集
   - 確認ダイアログ付き Webhook 削除
   - ブラウザ Push 通知の許可状態表示
   - 現在のブラウザの Push 登録状態表示
diff --git a/src/client/routes/NotificationMethodsView.jsx b/src/client/routes/NotificationMethodsView.jsx
index 4285601..c4a2437 100644
--- a/src/client/routes/NotificationMethodsView.jsx
+++ b/src/client/routes/NotificationMethodsView.jsx
@@ -1,4 +1,5 @@
 import { useCallback, useEffect, useState } from 'react';
+import * as Dialog from '@radix-ui/react-dialog';
 import { ArrowLeft, BellOff, BellRing, Link, Pencil, Plus, Trash2 } from 'lucide-react';
 import { request } from '../api/client.js';
 import { ConfirmDialog } from '../components/ConfirmDialog.jsx';
@@ -56,7 +57,9 @@ export function NotificationMethodsView({ onBack }) {
   const [vapidPublicKey, setVapidPublicKey] = useState('');
   const [currentPushStatus, setCurrentPushStatus] = useState('unchecked');
   const [form, setForm] = useState({ alias: '', url: '' });
-  const [editingId, setEditingId] = useState('');
+  const [editingWebhook, setEditingWebhook] = useState(null);
+  const [editForm, setEditForm] = useState({ alias: '', url: '' });
+  const [editDialogOpen, setEditDialogOpen] = useState(false);
   const [permission, setPermission] = useState(
     typeof Notification === 'undefined' ? 'unsupported' : Notification.permission,
   );
@@ -121,19 +124,12 @@ export function NotificationMethodsView({ onBack }) {
     setBusy(true);
     try {
       validateWebhookForm(form);
-      const endpoint = editingId
-        ? `/api/notification-methods/webhooks/${editingId}`
-        : '/api/notification-methods/webhooks';
-      await request(endpoint, {
-        method: editingId ? 'PATCH' : 'POST',
+      await request('/api/notification-methods/webhooks', {
+        method: 'POST',
         body: JSON.stringify({ alias: form.alias.trim(), url: form.url.trim() }),
       });
       setForm({ alias: '', url: '' });
-      setEditingId('');
-      showToast({
-        type: 'success',
-        message: editingId ? 'Webhookを更新しました' : 'Webhookを登録しました',
-      });
+      showToast({ type: 'success', message: 'Webhookを登録しました' });
       await loadMethods();
     } catch (err) {
       showToast({ type: 'error', message: err.message });
@@ -143,8 +139,38 @@ export function NotificationMethodsView({ onBack }) {
   }
 
   function startEdit(webhook) {
-    setEditingId(webhook.notificationMethodId);
-    setForm({ alias: webhook.alias, url: webhook.url });
+    setEditingWebhook(webhook);
+    setEditForm({ alias: webhook.alias, url: webhook.url });
+    setEditDialogOpen(true);
+  }
+
+  function handleEditDialogOpenChange(open) {
+    setEditDialogOpen(open);
+    if (!open) {
+      setEditingWebhook(null);
+      setEditForm({ alias: '', url: '' });
+    }
+  }
+
+  async function submitWebhookEdit(event) {
+    event.preventDefault();
+    if (!editingWebhook) return;
+
+    setBusy(true);
+    try {
+      validateWebhookForm(editForm);
+      await request(`/api/notification-methods/webhooks/${editingWebhook.notificationMethodId}`, {
+        method: 'PATCH',
+        body: JSON.stringify({ alias: editForm.alias.trim(), url: editForm.url.trim() }),
+      });
+      showToast({ type: 'success', message: 'Webhookを更新しました' });
+      handleEditDialogOpenChange(false);
+      await loadMethods();
+    } catch (err) {
+      showToast({ type: 'error', message: err.message });
+    } finally {
+      setBusy(false);
+    }
   }
 
   async function deleteWebhook(methodId) {
@@ -273,11 +299,50 @@ export function NotificationMethodsView({ onBack }) {
             </Field>
             <button className="primary" disabled={busy}>
               <Plus aria-hidden="true" size={18} />
-              {editingId ? '更新' : '登録'}
+              登録
             </button>
           </div>
         </form>
 
+        <Dialog.Root open={editDialogOpen} onOpenChange={handleEditDialogOpenChange}>
+          <Dialog.Portal>
+            <Dialog.Overlay className="dialog-overlay" />
+            <Dialog.Content className="dialog-content">
+              <Dialog.Title className="dialog-title">Webhookを編集</Dialog.Title>
+              <form className="dialog-form" onSubmit={submitWebhookEdit}>
+                <Field label="エイリアス名">
+                  <input
+                    value={editForm.alias}
+                    onChange={(event) => setEditForm({ ...editForm, alias: event.target.value })}
+                    placeholder="Slack 通知"
+                    maxLength="120"
+                    required
+                  />
+                </Field>
+                <Field label="URL">
+                  <input
+                    value={editForm.url}
+                    onChange={(event) => setEditForm({ ...editForm, url: event.target.value })}
+                    placeholder="https://hooks.slack.com/services/..."
+                    maxLength="2048"
+                    required
+                  />
+                </Field>
+                <div className="dialog-actions">
+                  <Dialog.Close asChild>
+                    <button className="secondary" type="button">
+                      キャンセル
+                    </button>
+                  </Dialog.Close>
+                  <button className="primary" disabled={busy || !editingWebhook}>
+                    更新
+                  </button>
+                </div>
+              </form>
+            </Dialog.Content>
+          </Dialog.Portal>
+        </Dialog.Root>
+
         <section className="panel">
           <h2>登録済みWebhook</h2>
           <div className="method-list">