PURPOSE: To correct balance by disposing balance rings each having an unbalance weight on the outer periphery of a spindle via vibrators, and rotating the balance rings up to balance positions by the vibration of the vibrators.

CONSTITUTION: A grinding wheel flange 4 is tightened on a spindle 3 of a grinder 1. A pair of vibrators 13, 14 each constituting of a piezoelectric element are provided, and a couple of balance rings 15, 16 are rotatably disposed. When rotating torque is generated due to deformation with application of a DC current to the vibrating rings (vibrators) 13, 14, the balance rings 15, 16 are rotated. A required turning amount of the balance rings 15, 16 of a balance corrector 10 is calculated on the basis of the maximum vibrating amount of the grinding wheel 9, and a controller outputs a correction signal to correct the balance of the grinding wheel 9. Therefore, responsiveness of balance correction is enhanced, and the constitution of the corrector can be simplified.