PURPOSE: To always correct the dispersion of the diameter of a grinding place based on the thermal deformation of a grinder by inserting the advance and retreat movement in the grindstone notching direction between grindstones to the traverse of the correction tool whose movement is controlled with a CNC control in accordance with the error between diameters of each grinding place of a work in advance.

CONSTITUTION: Measuring instruments 14, 15 measuring the diameter of each work are arranged at the grinding place of a work. A CNC control unit 21 having received a work measuring signal from the measuring instrument 14, 15 inserts the advance and retreat movement in the grindstone notching direction between grindstones 1, 2 to the traverse of the correction tool (rotary diamond) 18 whose movement is controlled by the CNC control according to the error between diameters of each grinding place of a work W in advance. The correction of error between the diameter D1, D2 of each grinding place of the work W is thus performed.