52 species assignable to 39 genera of Middle Permian (Midian in the Tethyan standard scale) foraminifers are distinguished in the limestone blocks exposed in Kaize, southern part of the Saku Basin, Nagano prefecture, central Japan. Faunal composition and biostratigraphic distribution of these taxa are described and discussed, in addition to systematic description of eleven species including Yabeina kaizensis based on the topotype materials. The ozawainellid genus, Primoriina is concluded to be probably a junior synonym of Sichotenella. The Kaize fauna is represented by (1) abundant occurrence of Yabeina kaizensis and Yabeina higoensis, (2) complete absence of genera assignable to Verbeekinidae and Staffellidae, (3) variable non-fusulinacean foraminifers consisting of 39 species assignable to 31 genera, and (4) occurrence of Robuloides, Dagmarita, and Postendothyra, characteristic of the Tethyan Upper Permian. These fora-minifers are important paleogeographically in relation to the faunal composition and taxonomic diversity of the Tethyan and Circum-Pacific regions in the late Middle Permian time.