PURPOSE: To prevent concentration of casting stress in a joint part and also, crystallization of coarse graphite in peripheral face of a hat part by restraining rapid cooling in the joint part between the hat part and a disk part in a cast iron-made disk plate raw material.

CONSTITUTION: At position corresponding to the joint part between the hat part and the disk part in the disk plate in a mold, a cover member 5 composed of an annular ceramic material providing a chiller, is set and molten metal is poured into the mold under this condition to cast the disk plate raw material 11 integratively combining the cover member 5. After this casting, the disk plate raw material 11 is taken out from the mold and rapidly cooled by spraying water.