diff --git a/index.html b/index.html
index 39cd067..e70752c 100644
--- a/index.html
+++ b/index.html
@@ -676,7 +676,11 @@ async function tryVoicevox(text) {
         headers: { 'Content-Type': 'application/json', 'Authorization': `Bearer ${apiKey}` },
         body: JSON.stringify({ text: preprocessText(text), speaker: ttsSpeaker }),
     });
-    if (!res.ok) return false;
+    if (!res.ok) {
+        const msg = res.status === 401 ? 'APIキーが無効です' : res.status === 503 ? 'VOICEVOXが起動していません' : `サーバーエラー (${res.status})`;
+        if (currentIdx === 0 && typeof showToast === 'function') showToast('VOICEVOX: ' + msg);
+        return false;
+    }
 
     const buf = await ctx.decodeAudioData(await res.arrayBuffer());
     if (!isPlaying) return true;
@@ -713,7 +717,9 @@ async function speak(text) {
     stopAudio();
 
     let vvOk = false;
-    try { vvOk = (await tryVoicevox(text)) === true; } catch(e) {}
+    try { vvOk = (await tryVoicevox(text)) === true; } catch(e) {
+        if (currentIdx === 0 && typeof showToast === 'function') showToast('VOICEVOX エラー: ' + (e.message || e));
+    }
 
     if (!isPlaying) return;
     if (vvOk) {