diff --git a/src/genesis/parsers/sheet_detector.py b/src/genesis/parsers/sheet_detector.py
new file mode 100644
index 0000000..1f55ec4
--- /dev/null
+++ b/src/genesis/parsers/sheet_detector.py
@@ -0,0 +1,51 @@
+from __future__ import annotations
+
+from typing import Any
+
+from genesis.data_models import SheetType
+
+# Sheet 名关键词（design §3.5.1，顺序即优先级）
+NAME_KEYWORDS: list[tuple[str, SheetType]] = [
+    ("機能", SheetType.FUNCTION),
+    ("画面", SheetType.SCREEN),
+    ("帳票", SheetType.REPORT),
+    ("テーブル", SheetType.DATABASE),
+    ("DB", SheetType.DATABASE),
+    ("インターフェース", SheetType.INTERFACE),
+    ("IF", SheetType.INTERFACE),
+    ("バッチ", SheetType.BATCH),
+    ("ジョブ", SheetType.BATCH),
+    ("マスタ", SheetType.MASTER),
+    ("コード", SheetType.MASTER),
+]
+
+# 表头关键词
+HEADER_KEYWORDS: list[tuple[str, SheetType]] = [
+    ("機能ID", SheetType.FUNCTION),
+    ("画面ID", SheetType.SCREEN),
+    ("帳票ID", SheetType.REPORT),
+    ("テーブルID", SheetType.DATABASE),
+    ("IF名", SheetType.INTERFACE),
+    ("バッチID", SheetType.BATCH),
+]
+
+
+def _name_hit(sheet_name: str) -> SheetType | None:
+    for kw, st in NAME_KEYWORDS:
+        if kw in sheet_name:
+            return st
+    return None
+
+
+def _header_hit(matrix: list[list[Any]]) -> SheetType | None:
+    for row in matrix[:3]:
+        for cell in row:
+            if isinstance(cell, str):
+                for kw, st in HEADER_KEYWORDS:
+                    if kw in cell:
+                        return st
+    return None
+
+
+def detect_sheet_type(sheet_name: str, matrix: list[list[Any]]) -> SheetType:
+    return _name_hit(sheet_name) or _header_hit(matrix) or SheetType.GENERIC
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diff --git a/tests/test_sheet_detector.py b/tests/test_sheet_detector.py
new file mode 100644
index 0000000..c9a1867
--- /dev/null
+++ b/tests/test_sheet_detector.py
@@ -0,0 +1,21 @@
+from genesis.data_models import SheetType
+from genesis.parsers.sheet_detector import detect_sheet_type
+
+
+def test_detect_by_sheet_name():
+    assert detect_sheet_type("機能一覧", []) == SheetType.FUNCTION
+    assert detect_sheet_type("画面一覧", []) == SheetType.SCREEN
+    assert detect_sheet_type("帳票一覧", []) == SheetType.REPORT
+    assert detect_sheet_type("DB定義", []) == SheetType.DATABASE
+    assert detect_sheet_type("IF定義", []) == SheetType.INTERFACE
+    assert detect_sheet_type("バッチ一覧", []) == SheetType.BATCH
+    assert detect_sheet_type("コード管理", []) == SheetType.MASTER
+
+
+def test_detect_by_header_keyword():
+    matrix = [["帳票ID", "帳票名"], ["TB1", "月次"]]
+    assert detect_sheet_type("補充シート", matrix) == SheetType.REPORT
+
+
+def test_unknown_is_generic():
+    assert detect_sheet_type("メモ", [["随筆"]]) == SheetType.GENERIC
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