Eighty-four species of fossil ostracodes are described for the first time in four sediment samples from the lower Pleistocene Masuda Formation（ca．1.4-1.0 Ma），Tanega-shima Island，southern Japan．The dominant species are Neonesidea oligodentata，Aurila corniculta，Xestoleberis，hanaii，Schizocythere kishinouyei，and Cytheropteron miurense，which live on near-shore sand or algae under the influence of open water currents．Upper to middle sublittoral species，such as Argilloecia spp.，Cytheropteron uchioi，and Cytherelloidea hanaii，are also present．Therefore，the depositional environment of the Masuda Formation was an upper to middle sublittoral zone under the strong influence of open near-shore currents．The fossil ostracode assemblages are more similar to Recent warm temperate water assemblages found around the Honshu and Shikoku Islands than to the tropical water assemblages found in the Pleistocene to Holocene deposits of the Ryukyu Islands．