The metamorphic grade of kerogen in the Paleozoic and Mesozoic strata around the Hikami and Kesengawa granites was determined from the crystallinity using X-ray diffraction and vitrinite reflectivity. L_c(002) of the kerogen ranges from 15 to >1000 Å and increases with approaching to the Kesengawa granite pluton intruded in the Cretaceous age. The metamorphic zones of the kerogen are divided into L_c(002)<50 Å, 50-200 Å, and >200 Å zones. These zones are arranged around the Kesengawa granite and have no relation to the stratigraphic boundaries. Rmax values of vitrinite from L_c(002)<50 Å zone are 4.65-6.37%, which are meta-anthracite in rank of the German classification. The Hikami granite is surrounded by the Silurian to the Cretaceous strata which is less than 50 Å in L_c(002). There are no thermal effects in the strata adjacent to the Hikami granite. This suggests that the Hikami granite belongs to the Pre-Silurian basement rocks.