PURPOSE: To remove bar-like cores made of an easily cuttable blank material without punching directly holes in a metallic mold product for casting to punch pores and to facilitate a punching operation by fixing said cores between a top mold and a bottom mold for casting, and cutting the cores with a drill after charging a molten metal in the mold and solidifying the same.

CONSTITUTION: Graphite bars 3 having the same diameter as the diameter of pores are fixed between a top mold 1 and a bottom mold 2 in the positions for punching the desired pores. A molten metal to be made into a metallic mold product 6 for casting is charged into the charging ports 7, 7 for molten metal of the mold 1. A top mold flask 4 is removed and the product 6 is removed after the product 6 solidifies, then the bars 3 embedded therein are cut away with a drill or the like, whereby the metallic mold for casting having the pores of a desired bore is obtd. The bars 3 are used as a core and any blank material which can be easily removed by a drill or the like is equally well.