The Osaka Group is typical of the Plio-Pleistocene Series in Japan. The correlation of paleomagnetic stratigraphy and biostratigraphy gives a clear picture of the Quarternary history of the Group. The Komyoike volcanic ash layer distributed only in the Senpoku area, in the southern part of Osaka Prefecture is shown to have normal polarity at 1.1 million years (fission track age). The remanent magnetizations of more than one hundred oriented samples collected in sequence from the out-crop sediments intercalated with the Komyoike volcanic ash bed were measured. Paleomagnetic results after magnetic cleaning show that the sedimentary sequence is divided into three distinct zones by changes in the remanent polarity.