---
title: "Look up a Japanese postal code / 郵便番号から住所"
method: GET
path: "/v1/postal-codes/lookup"
---

# Look up a Japanese postal code / 郵便番号から住所

`GET /v1/postal-codes/lookup`

## Request

- Base URL: `https://biz.ossalt.jp`
- URL: `https://biz.ossalt.jp/v1/postal-codes/lookup`
- Auth: none declared

Look up the address (prefecture, city, town) for a 7-digit Japanese postal code, from Japan Post data. Accepts forms like 1000001, 100-0001 or 〒100-0001. One code can cover several towns; all are returned. `town_detail` holds the parenthesized part as written by Japan Post (e.g. chome ranges or building floors). If the code is a business-specific code (大口事業所個別番号) or a PO box code, the business is returned in `offices`. / 郵便番号から住所（都道府県・市区町村・町域）。日本郵便のデータ。1つの郵便番号に町域が複数あれば、すべて返す。事業所の個別郵便番号なら、事業所名と所在地を offices に返す。

## Query parameters

- `postal_code` string, required: 7-digit postal code, hyphen optional / 郵便番号（7桁、ハイフンは任意）

## Response `200`

OK

- Answer
  - `result` object, required: The answer / 結果
  - `source` object, required: Source and verification / 出典と照合の状況
  - `as_of` string, required: Reference date in Japan time (YYYY-MM-DD) / 基準日（日本時間）
  - `notes` string[], required: Assumptions such as estimated values / 前提（見込みの値など）
  - `flags` string[], required: `flags` holds machine-readable codes: `estimated` (a value is an estimate, e.g. a future equinox day — tell the user), `unverified` (year not yet checked against Cabinet Office data — tell the user), `assumes_current_era` (a future date written in the current era — tell the user), `outside_era` (the era date given is outside that era), `weekday_mismatch`, `closed` (the company's registry record is closed — tell the user), `excluded_from_search`, `truncated`, `not_found`, `exact_match_only`, `partial`, `ambiguous`, `city_not_found`, `ambiguous_city`.

## Other responses

- `400`: Invalid parameters / 入力の誤り
- `429`: Too many requests / 呼び出しが多すぎます
- `503`: Data unavailable / データを読めない

---

[API](https://skmtc.dev/ossalt/apis/japan-business-tools.md) · [All operations](https://skmtc.dev/ossalt/apis/japan-business-tools/llms.txt) · [OpenAPI document](https://skmtc.dev/ossalt/apis/japan-business-tools/revisions/8bb72a25e175?raw)