The floras of the Miocene Kani, Mizunami, Iwamura, Tomikusa and Shidara Group in the eastern part of the Setouchi region are analyzed for vegetational types. The vegetational histry of the area is summarized as follows.[table] The mean annual temperature of the area was 10°～13℃ for 20-22 Ma, 10°～13℃ for 18-20 Ma, 13°～16℃ for 16.5-18 Ma and 15°～20℃ for 14-16.5 Ma. The cold month mean for 14-16.5 Ma was 3°～10℃ which is the highest of all, and for 18-20 Ma was -2°～1℃ which is the lowest of all. The largest annual precipitation, 1,200～4,000mm is found for 14-16.5 Ma, and the smallest annual precipitation, 800～1,000mm for 18-20 Ma. The close floristic resemblance between southwest Honshu and Korea of 20-22 Ma supports the idea that the two areas were geographically connected during this age. On the other hand for 14-16.5 Ma the remarkable floristic difference between them and increase of the winter precipitation in southwest Honshu suggest the separation of them by a sea in this age.