a grinding tool with an eccentric rotation shaft of a grinding disc with attached grinding material installed via a bearing at a position that is shifted from the central drive shaft line of a rotating disc fixed on a drive shaft , comprises a clutch in which a grinding disc - side clutch component member installed on the grinding disc or on the eccentric rotation shaft that is fixed to the grinding disc and a rotating disc - side clutch component member installed on the rotating disc are linked via a sliding surface capable of sliding and of transmitting the drive force . the rotation rate of the grinding disc is limited to a stable range of rotation rates , preventing extreme elevation in the rotation rate and extreme reduction in the rotation rate ; the workpiece is ground efficiently ; and the tool does not generate marks or patterns on the ground surface .