diff --git a/src/sing/domain.ts b/src/sing/domain.ts
index 4d0f9bf54f..62a4b9b9d5 100644
--- a/src/sing/domain.ts
+++ b/src/sing/domain.ts
@@ -505,8 +505,8 @@ type PhonemeTiming = {
 };
 
 export type PhonemeTimingEdit = {
-  phonemeIndex: number; // ノート内での音素の順番
-  offset: number; // 単位は秒
+  phonemeIndexInNote: number;
+  offsetSeconds: number;
 };
 
 export type PhonemeTimingEditData = Map<NoteId, PhonemeTimingEdit[]>;
@@ -667,7 +667,7 @@ function applyPhonemeTimingEditToPhonemeTimings(
   phonemeTimingEditData: PhonemeTimingEditData,
   frameRate: number,
 ) {
-  let phonemeIndex = 0;
+  let phonemeIndexInNote = 0;
   for (let i = 0; i < phonemeTimings.length; i++) {
     const phonemeTiming = phonemeTimings[i];
     const prevPhonemeTiming = getPrev(phonemeTimings, i);
@@ -677,9 +677,9 @@ function applyPhonemeTimingEditToPhonemeTimings(
       prevPhonemeTiming == undefined ||
       phonemeTiming.noteId !== prevPhonemeTiming.noteId
     ) {
-      phonemeIndex = 0;
+      phonemeIndexInNote = 0;
     } else {
-      phonemeIndex++;
+      phonemeIndexInNote++;
     }
 
     if (phonemeTiming.phoneme === "pau") {
@@ -693,8 +693,11 @@ function applyPhonemeTimingEditToPhonemeTimings(
       continue;
     }
     for (const phonemeTimingEdit of phonemeTimingEdits) {
-      if (phonemeTimingEdit.phonemeIndex === phonemeIndex) {
-        const offsetFrame = secondToFrame(phonemeTimingEdit.offset, frameRate);
+      if (phonemeTimingEdit.phonemeIndexInNote === phonemeIndexInNote) {
+        const offsetFrame = secondToFrame(
+          phonemeTimingEdit.offsetSeconds,
+          frameRate,
+        );
         const roundedOffsetFrame = Math.round(offsetFrame);
 
         phonemeTiming.startFrame += roundedOffsetFrame;
@@ -702,11 +705,14 @@ function applyPhonemeTimingEditToPhonemeTimings(
           prevPhonemeTiming.endFrame = phonemeTiming.startFrame;
         }
       } else if (
-        phonemeTimingEdit.phonemeIndex === phonemeIndex + 1 &&
+        phonemeTimingEdit.phonemeIndexInNote === phonemeIndexInNote + 1 &&
         nextPhonemeTiming?.phoneme === "pau"
       ) {
         // NOTE: 休符のpauseは休符の直前のノートに含まれる音素として扱う
-        const offsetFrame = secondToFrame(phonemeTimingEdit.offset, frameRate);
+        const offsetFrame = secondToFrame(
+          phonemeTimingEdit.offsetSeconds,
+          frameRate,
+        );
         const roundedOffsetFrame = Math.round(offsetFrame);
 
         phonemeTiming.endFrame += roundedOffsetFrame;
diff --git a/tests/unit/domain/sing/applyPhonemeTimingEdit.spec.ts b/tests/unit/domain/sing/applyPhonemeTimingEdit.spec.ts
index 5ce7ea1677..932a948eb4 100644
--- a/tests/unit/domain/sing/applyPhonemeTimingEdit.spec.ts
+++ b/tests/unit/domain/sing/applyPhonemeTimingEdit.spec.ts
@@ -126,8 +126,8 @@ describe("applyPhonemeTimingEditAndAdjust", () => {
 
   it("音素タイミング編集が適用される", () => {
     const phonemeTimingEditData = new Map<NoteId, PhonemeTimingEdit[]>([
-      [noteIds[1], [{ phonemeIndex: 0, offset: -3 / frameRate }]],
-      [noteIds[4], [{ phonemeIndex: 1, offset: 6 / frameRate }]],
+      [noteIds[1], [{ phonemeIndexInNote: 0, offsetSeconds: -3 / frameRate }]],
+      [noteIds[4], [{ phonemeIndexInNote: 1, offsetSeconds: 6 / frameRate }]],
     ]);
     const expectedPhraseQueries = structuredClone(phraseQueries);
     expectedPhraseQueries[0].phonemes[2].frameLength -= 3;
@@ -146,8 +146,8 @@ describe("applyPhonemeTimingEditAndAdjust", () => {
 
   it("音素が重ならないように音素タイミングが調整される", () => {
     const phonemeTimingEditData = new Map<NoteId, PhonemeTimingEdit[]>([
-      [noteIds[1], [{ phonemeIndex: 1, offset: -12 / frameRate }]],
-      [noteIds[2], [{ phonemeIndex: 2, offset: 60 / frameRate }]],
+      [noteIds[1], [{ phonemeIndexInNote: 1, offsetSeconds: -12 / frameRate }]],
+      [noteIds[2], [{ phonemeIndexInNote: 2, offsetSeconds: 60 / frameRate }]],
     ]);
     const expectedPhraseQueries = structuredClone(phraseQueries);
     expectedPhraseQueries[0].phonemes[2].frameLength -= 6;
@@ -167,8 +167,8 @@ describe("applyPhonemeTimingEditAndAdjust", () => {
 
   it("pauseのフレーム長が1以上になるように音素タイミングが調整される", () => {
     const phonemeTimingEditData = new Map<NoteId, PhonemeTimingEdit[]>([
-      [noteIds[3], [{ phonemeIndex: 1, offset: -60 / frameRate }]],
-      [noteIds[5], [{ phonemeIndex: 2, offset: 60 / frameRate }]],
+      [noteIds[3], [{ phonemeIndexInNote: 1, offsetSeconds: -60 / frameRate }]],
+      [noteIds[5], [{ phonemeIndexInNote: 2, offsetSeconds: 60 / frameRate }]],
     ]);
     const expectedPhraseQueries = structuredClone(phraseQueries);
     expectedPhraseQueries[1].phonemes[0].frameLength -= 39;