A time sequence of grain size distributions from the Pleistocene sediments in Lake Biwa, located in the central part of Japan (35¿ N, 136¿ E), has dominant periodicities of 41,000, 23,000, and 19,000 years which are very close to those predicted from the astronomical theory of paleoclimate introduced by Milankovitch. The time variation of the grain size is very similar to that of insolation of caloric summer in the Northern Hemisphere.