PURPOSE: To enable abrasive works for a curved face to be performed not by manual work but with machine abrasive work, by mounting a grindstone in a form of universal joint to the output power shaft of a motor.

CONSTITUTION: To a motor output shaft 2, a spherial body shaft 5 is mounted, and to a tip of the spherical body shaft 5, a spherical body 7 is provided. Said spherical body 7 is housed inside a ball supporting member 4 and the spherical body shaft 5 is connected to the ball supporting member 4 with a resilient material of coil spring 8 or the like. A spherical hole 4a of the ball supporting member 4 is formed in almost the same diameter as that of the spherical body 7 to permit the mutual sliding motion between the spherical body and the ball supporting member. To a lower side of the ball supporting member 4, is mounted a grindstone 3 to which rotary power is transmitted from the motor output shaft 2 through the coil spring 8. Hard rubber may be used as the resilient material 8. In this way, a grinder with the grindstone 3 can be driven in a rotary motion in a form of universal joint, state, and can perform abrasive work for a plane and curved face not by hand work, if it is mounted to a suitable supporting device.