To provide a grinding wheel correcting device having a simple and inexpensive deviation correcting structure for easy and highly precise run out correction in a working plane on the outer periphery of a rotary diamond when mounting a new rotary diamond on a spindle.

The grinding wheel correcting device has such an annular truer configuration that the axis of the spindle 12 of the rotary diamond 10 is arranged in a plane including the axis of a grinding wheel spindle 3 of a grinding wheel 2 and a run out removing truer for removing run out in a working plane on the outer periphery of the rotary diamond 10 is provided coaxially on the grinding wheel spindle 3. Therefore, the run out correction of the rotary diamond 10 is carried out on a machine as it stands on the spindle 12.