牛深市是位于日本熊本县天草群岛南部的一个已废除的城市，于2006年3月27日与周围的城镇合并为天草市。

Ushibuka(牛深市,Ushibuka-shi) was a city located in Kumamoto Prefecture, Japan. The city was founded on April 1, 1954.

As of 2003, the city had an estimated population of 17,429 and the density of 194.17 persons per km². The total area was 89.76 km².

On March 27, 2006, Ushibuka, along with the city of Hondo, and the towns of Amakusa, Ariake, Goshoura, Itsuwa, Kawaura, Kuratake, Shinwa and Sumoto (all from Amakusa District), was merged to create the new city of Amakusa and no longer exists as an independent municipality.