diff --git a/packages/page/package.json b/packages/page/package.json
index f21ae3b..5d1126e 100644
--- a/packages/page/package.json
+++ b/packages/page/package.json
@@ -32,7 +32,13 @@
   "keywords": [
     "vite-plugin-minissg"
   ],
+  "dependencies": {
+    "debug": "^4.3.4"
+  },
   "peerDependencies": {
     "vite-plugin-minissg": "^3.0.0"
+  },
+  "devDependencies": {
+    "@types/debug": "^4.1.12"
   }
 }
diff --git a/packages/page/src/debug.ts b/packages/page/src/debug.ts
new file mode 100644
index 0000000..1dda1e3
--- /dev/null
+++ b/packages/page/src/debug.ts
@@ -0,0 +1,38 @@
+import createDebug from 'debug'
+import type { Awaitable } from '../../vite-plugin-minissg/src/util'
+
+const d = createDebug('minissg:page')
+export const debug = d.enabled ? d : undefined
+
+const sleep = (msec: number): PromiseLike<undefined> =>
+  new Promise(resolve => {
+    setTimeout(() => {
+      resolve(undefined)
+    }, msec)
+  })
+
+const debugTimerPeriod = 3000
+
+const debugTimerImpl = <X>(
+  task: () => PromiseLike<X>,
+  callback: (
+    debug: typeof d,
+    dt: number,
+    when: 'start' | 'middle' | 'end'
+  ) => Awaitable<void>
+): PromiseLike<X> => {
+  const promise = task().then(x => ({ done: x }))
+  const t1 = performance.now()
+  return Promise.resolve(callback(d, 0, 'start')).then(async () => {
+    for (;;) {
+      const result = await Promise.race([promise, sleep(debugTimerPeriod)])
+      const t2 = performance.now()
+      await callback(d, t2 - t1, result != null ? 'end' : 'middle')
+      if (result != null) return result.done
+    }
+  })
+}
+
+export const debugTimer = d.enabled
+  ? debugTimerImpl
+  : <X>(f: () => PromiseLike<X>) => f()
diff --git a/packages/page/src/tree.ts b/packages/page/src/tree.ts
index af225f3..f84e953 100644
--- a/packages/page/src/tree.ts
+++ b/packages/page/src/tree.ts
@@ -1,6 +1,7 @@
 import { AsyncLocalStorage } from 'node:async_hooks'
 import type * as minissg from '../../vite-plugin-minissg/src/module'
 import { type Awaitable, raise } from '../../vite-plugin-minissg/src/util'
+import { debugTimer } from './debug'
 import { isAbsURL, defineProperty, createObject, objectAssign } from './util'
 import { type Delay, delay } from './delay'
 import { Memo } from './memo'
@@ -329,7 +330,17 @@ class TreeNodeImpl<Base, This extends Base, Impl> {
     const render1 = async (): R => await this.module.render(mod)
     const render2 = async (): R => await currentNode.run(this, render1)
     const render3 = async (): R => await this.memo.run(render2)
-    return { default: delay(render3) }
+    const render = debugTimer(render3, (debug, dt, when) => {
+      const path = `/${c.moduleName.path}`
+      if (when === 'start') {
+        debug('start rendering %s', path)
+      } else if (when === 'middle') {
+        debug('now rendering %s (+%s sec)', path, (dt / 1000).toFixed(3))
+      } else {
+        debug('rendering %s finished (%s sec)', path, (dt / 1000).toFixed(3))
+      }
+    })
+    return { default: delay(render) }
   }
 }
 
diff --git a/pnpm-lock.yaml b/pnpm-lock.yaml
index d6ab764..9be5eba 100644
--- a/pnpm-lock.yaml
+++ b/pnpm-lock.yaml
@@ -220,9 +220,16 @@ importers:
 
   packages/page:
     dependencies:
+      debug:
+        specifier: ^4.3.4
+        version: 4.3.4
       vite-plugin-minissg:
         specifier: workspace:^
         version: link:../vite-plugin-minissg
+    devDependencies:
+      '@types/debug':
+        specifier: ^4.1.12
+        version: 4.1.12
 
   packages/render-preact:
     dependencies: