Clay minerals in the core sediments from Lake Shinji were analyzed．Vertical and lateral distributions of clay minerals in Lake Shinji were clearified，and can be summarized as follows；
1）Smectite，kaolinite，vermiculite，chlorite，illite and halloysite，were major clay minerals．
2）In the eastem area，relative abundance of smectite changes drastically at the depth of 40cm to be more abundant in the deeper zone．The depth，where the relative abundance of smectite starts to increase，tends to be deeper from the east to the west．This drastic change of clay mineral abundance is possibly corresponding to the invasion of Hii river into Lake Shinji in 1635's．
3）Kaolinite decreases with depth and its tendency is reversal to that of smectite．