PURPOSE: To increase contact points between a grinding wheel surface and a workpiece, to reduce the vibrations of a bearing and the grinding wheel and to make stable contacts between the grinding wheel surface and the workpiece by forming a cup grinding wheel in a dual grinding particle structure having inner and outer ring layers.

CONSTITUTION: In a cup grinding wheel 10 used for a model mirror grinder, that is, an infeeding type mirror grinder, a grinding particle layer 26 is fixed to a base metal 25. In this case, the cup grinding wheel 10 is formed in a dual grinding particle structure having an inner ring layer 36 and an outer ring layer 35. The grinding wheel surfaces of the inner and outer ring layers 36 and 35 are disposed on the same face. Also, the grinding particle layers of the inner and outer ring layers 36 and 35 are set almost with the same width. Thus, contact points between the grinding wheel surface and a workpiece are increased, the vibrations of a bearing and the griding wheel are reduced and a contact between the grinding wheel surface and the workpiece is made stable.