We used composition of plant macrofossil assemblages obtained mainly from theOsaka Group in central Japan to reconstruct the palaeoclimate between the late Pliocene (about 3.3m.y. B.P.) and the middle Pleistocene (about 0.4 m.y. B.P.). The warmest climate of the periodwas before 3.0 m.y. B.P. Cool-temperate elements increased and subtropical elements decreasedbetween 3 m.y. B.P. and 2.7 m.y. B.P., indicating the first climatic deterioration. The firstoccurrence of subarctic elements characterizes the Plio-Pleistocene boundary as a severe coldstage. After 1.1 m.y. B.P., climatic fluctuation occurred at less than 100,000 year intervals. Asevere cold stage occurred just after the Jaramillo event (about 0.8 m.y. B.P.). The warmest stagein the middle Pleistocene occurred at about 0.5 m.y. B.P. With it evergreen broad-leaved forestexpanded into central Japan. The climatic curves reconstructed from plant macrofossils parallel theclimatic changes reconstructed from loess - paleosol stratigraphy in Central China, radiolarianfaunal stratigraphy in the north Pacific deep sea drilling core, oxygen-isotope data in the NorthPacific, and pollen spectra in western Europe. We used composition of plant macrofossil assemblages obtained mainly from the Osaka Group in central Japan to reconstruct the palaeoclimate between the late Pliocene (about 3.3 my BP) and the middle Pleistocene (about 0.4 my BP). The warmest climate of the period was before 3.0 my BP Cool-temperate elements increased and subtropical elements decreasedbetween 3 my BP and 2.7 my BP, indicating the first climatic deterioration. The firstoccurrence of subarctic elements characterizes the Plio-Pleistocene boundary as a severe cold stage. After 1.1 my BP, climatic occurred occurred at less than than 100,000 years intervals. Asevere cold stage occurred just after the Jaramillo event (about 0.8 my BP). The warmest stagein the middle Pleistocene occurred at about 0.5 my BP With it evergreen broad-leaved forestexpanded into central Japan. The climatic curves reconstructed from plant macrofossils parallel theclimatic changes reconstructed from loess - paleosol stratigraph y in Central China, radiolarianfaunal stratigraphy in the north Pacific deep sea drilling core, oxygen-isotope data in the North Pacific, and pollen spectra in western Europe.