The Takurayama Volcano located at the border of the Kyoto and Hyogo Prefectures is composed of basalt lava flows and scoria beds forming a lava plateau named Yakunogahara, and of a scoria cone on the lava plateau, that is Mt. Takurayama. The age of the activity of the Takuraya Volcano is the same as that of the Yakunogahara Formation which is late Middle to early Late Pleistocene, i.e., the period between the depositions of Ma8 in the Osaka Group and the Middle Terrace deposits. Results of the electric and seismic prospectings reveal the presence of the basement high of NS trend below the lava plateau, suggesting that the Makigawa River had not run down westward across the Yakunogahara before the eruption, as had been formerly insisted by Ueji (1925) and Miyajima et al. (1981). The basalt lava flows are divided into the Ogura, Kinuzuri and Takurayama lavas in ascending order. The Ogura lava flowed eastward from the basement high. The Kinuzuri lava flowed to the both sides of the high overlying a part of the Ogura lava. And the Takurayama lava flowed from the vicinity of Mt. Takurayama into the erosional valleys along the contact between the basement rocks and the Kinuzuri lava. The scoria cone was formed after the eruption of the lavas above the basement high. Each of three basalts is chemically classified into the alkali basalt. The chemical compositions of Pleistocene basaltic rocks in the eastern part of the San'in Province including the basalts of Takurayama Volcano are similar in each other. These basaltic rocks are characteristically free from ultrabasic xenoliths, and they are richer in Na2O and A12O3 and poorer in K20 and MgO than the ultrabasic xenoliths-bearing basalts in the Chugoku District. Therefore, we wish to designate the former as basalts of the Eastern San'in type and the latter as those of the Tsuyama-Abu type.