PURPOSE: To manufacture a desired metal mold accurately in a short time by letting a formed stone shift in a spare cup part, and grinding a spare projection part or spare groove.

CONSTITUTION: A first formed stone 10a is inserted into a cupped spare metal mold 1 while rotating it, and this formed stone 10a is travels in parallel with a shaft center of the spare metal mold 1 toward a bottom part from an opening end of the spare metal mold 1, and a spare projection part 4 of the spare metal mold 1 is ground for rough finish as leaving its finish-grinding allowance behind. Next, a second formed stone 10c is inserted into a spare cup part 3 of the spare metal mold 1 while rotating it, and the second formed stone 10c is traveled in parallel with the shaft center of the spare metal mold toward the bottom part from the opening end of the spare metal mold 1. With this second formed stone 10c, the spare projection strip part 4 is ground for finishing, securing a desired cupped metal mold.