The Miocene Morozaki Group spreads across the Chita Peninsula in Aichi prefecture, Central Honshu, Japan, and was deposited between 18 to 15 Ma. Using foraminiferal archives contained in samples from the Katana outcrop at the tip of the Chita Peninsula, we aimed to verify whether the Chita Peninsula used to be in the deep ocean. We used various techniques such as the planktonic / total ratio (P/T) method and faunal analysis. Faunal analysis on mollusks from the same outcrop was also undertaken in order to obtain better data. From these experiments, we estimate the paleodepth of the Morozaki Group to have been between 100 to 2000 meters below sea level, and that the Chita Peninsula sediments were deposited in the deep ocean.