The Main Zone of the Hidaka Metamorphic Belt is an uplifted crustal section of island arc type. The crust was formed during early Tertiary time, as a result of collision between two arc-trench systems of Cretaceous age. The crustal metamorphic sequence is divided into four metamorphic zones (I to IV), in which zone IV is in the granulite facies. A detailed study of the evolution of the Hidaka Belt, based on a revised P-T-t analysis of the metamorphic rocks, notably a newly found staurolite-bearing granulite, confirms a prograde isobaric heating path, after a supposed event of tectonic thickening of accretion sedimentary and oceanic crustal rocks. During the peak metamorphic event (ca. 52.6 Ma), the regional geothermal gradient attained 30 to 40 °C/km, and the highest P, T condition obtained from the lowest part of the granulite unit is 830 °C, 7kb. In this part, X_H2O of Gt-Opx-Cd gneiss is about 0.15 and that of Gt-Cd-Bt gneiss is 0.4. The P-T-X_H2O condition of the granulite unit is well within a field where fluid-present partial melting of pelitic and greywacke metamorphic rocks take place. This is in harmony with the restitic nature of the Gt-Opx-Cd gneiss in the lowest part of the granulite unit. The possibility that partial melting took place in the Main Zone is significant for the genesis of the peraluminous (S-type) granitic rocks within it. The S-type granitic rocks in this zone are Opx-Gt-Bt tonalite in granulite zone, Gt-Cd-Bt tonalite in amphibolite zone, and Cd-Bt-Mus tonalite in the Bt-Mus gneiss zone. The mineralogical and chemical natures of these strongly peraluminous tonalitic rocks permit us to regard them to have been derived from S-type granitic magma generated by crustal anatexis of pelitic metamorphic rocks in deeper crust.