Postal Code 378-0021 – Iwamotomachi, Gumma Ken

Postal Code 378-0021 for Iwamotomachi, Gumma Ken is part of the Japan postal code system, which uses a numeric code of 7 digits (e.g. 123-4567). Addresses here are organised as Prefecture → Municipality → Ward / District / Locality.

Administratively it is recorded in Gumma Ken within Japan. Postal codes are assigned by delivery route rather than by administrative boundary, so a single code can cover more than one locality and a locality can fall under several codes.

No building-level records are held for this code in the imported dataset, so only the code and its location details are shown. The absence of records does not mean the postal code is unused.

Couriers, e-commerce checkout forms and address autocomplete tools all rely on the postal code to route mail and to check that a stated address matches the code. Because a postal code identifies a delivery area rather than a single building, two addresses that share the same code can still be some distance apart.

Always write Japan Postal Code in full when completing a form, including any leading zero. Enter a valid Japanese postal code, e.g. 123-4567. Data source: a third-party open dataset. This is a reference snapshot, not a live government feed, so confirm the code with the sender, carrier or postal authority before relying on it.