diff --git a/PythonProj/ScanOCR/build/build_package.py b/PythonProj/ScanOCR/build/build_package.py
index 6e9db456..00e026c5 100644
--- a/PythonProj/ScanOCR/build/build_package.py
+++ b/PythonProj/ScanOCR/build/build_package.py
@@ -105,6 +105,24 @@ def setup_python(script_dst: Path, tmp_dir: Path) -> None:
     )
 
 
+SEVEN_ZIP_FALLBACK_PATHS = (
+    r"C:\Program Files\7-Zip\7z.exe",
+    r"C:\Program Files (x86)\7-Zip\7z.exe",
+)
+
+
+def find_7zip_exe() -> str:
+    found = shutil.which("7z")
+    if found:
+        return found
+    for candidate in SEVEN_ZIP_FALLBACK_PATHS:
+        if Path(candidate).exists():
+            return candidate
+    raise RuntimeError(
+        "7-Zip（7z.exe）が見つかりません。PATHに通すか、標準的な場所にインストールしてください。"
+    )
+
+
 def setup_tesseract(script_dst: Path, tmp_dir: Path) -> None:
     tools_dst = script_dst / "tools" / "tesseract"
     tools_dst.mkdir(parents=True)
@@ -112,10 +130,11 @@ def setup_tesseract(script_dst: Path, tmp_dir: Path) -> None:
     installer_path = tmp_dir / "tesseract-setup.exe"
     download(TESSERACT_INSTALLER_URL, installer_path)
 
+    seven_zip_exe = find_7zip_exe()
     extract_dir = tmp_dir / "tesseract-extract"
     extract_dir.mkdir()
     subprocess.run(
-        ["7z", "x", str(installer_path), f"-o{extract_dir}", "-y"],
+        [seven_zip_exe, "x", str(installer_path), f"-o{extract_dir}", "-y"],
         check=True,
     )
     for item in extract_dir.iterdir():