An ammonoid fauna comprising eight species belonging to seven genera (Agathiceras, Neoglaphyrites, Emilites, Somoholites, Marathonites, Eoasianites and Metapronorites) is described from the Uyamano Formation (Taishaku Limestone) at Miharanoro in the Akiyoshi Belt, Southwest Japan. The fauna includes two new species: Neoglaphyrites discoidalis and Somoholites miharanoroensis. The genera Emilites, Somoholites, Marathonites, and Metapronorites are described from Japan for the first time. From the coexisting interval of these seven genera, the age of the Miharanoro fauna is between the Kasimovian and Asselian, being very probably Asselian because some species show close resemblance to those known from Asselian strata. This is the most diverse early Permian ammonoid fauna ever known from Japan.