PURPOSE: To obtain go stones of good quality with ease by pressing a pressure tool against a raw go stone both sides of which are worked to be arc faces by a grinder, holding the raw go stone between the tool and a chuck and grinding the peripheral edge thereof.

CONSTITUTION: A raw go stone one side of which is ground to be of arc face by a grinder 6 is passed from one chuck 5 to the other 4 both provided face to face on the same central line of rotation and then the other side thereof is ground also to be of arc face. After that, a long arm 10 provided on a support axis in parallel with the center line of chucks 4 and 5 being rotated and moved slidably to the side of a short arm provided on the support axis, a go-stone pressing tool 12 of the long arm 10 is pressed against the raw go stone held by the chuck 4, thereby the go stone being held between the tool 12 and the chuck 4. Then, the peripheral edge of the raw go stone with both sides worked to be of arc face is ground by a grinder 13 provided at the tip of the short arm, thus a high-grade go stone being finished up.