To improve the flatness of the ground surface of a material to be polished and to perform precise polishing without generating tiny damages on the polished surface by friction-cutting and correcting craters on a surface caused by the wear of a pitch disk during the polishing of the material to be ground such as an optical crystal or an optical glass.

Imbalanced weight parts 16 are loaded in both ends of a dresser member 14 formed to be nearly cylindrical, the dresser member 14 is brought into contact with a stopper member 12 fixed in a polishing device main body 3 and mounted with play on the upper surface of a pitch disk 6 so as to cross the pitch disk in the vicinity of the rotational center of the pitch disk 6, and then the pitch disk 6 is rotated. By a polished material holding device 8, a material A to be polished is brought into contact with the upper surface of the pitch disk and polished.