PURPOSE: To find a distance ranging from a spindle center to a diamond tip without entailing any effect of thermal displacement in a headstock by installing a detecting-measuring arm member which measures the extent of displacement at the diamond tip of a dress position and being shifted to a measuring position and a second shunting position around the spindle.

CONSTITUTION: A dresser is turned round so as to make a tip of diamond 16 be situated on an infeed axis passing through a cutting point, performing a job for wheel dressing and truing, and an infeed axis coordinate value of a wheel spindle stock at time of this wheel dressing termination is stored in memory. Next, a detecting and measuring arm 22 is turned round a spindle, positioning a sensor 23 to a measuring position, and the extent of displace ment in the diamond 16 is detected and measured. Then, a distance ranging from the spindle center to the diamond tip is found out of this displacement, and this given distance is com pared with the infeed axis coordinate value of the wheel spindle stock at time of wheel dressing termination, thereby finding a compensation value at an operational part 34, and a machining zero position compensation for an infeed axis is performed, through which the distance of up to the diamond tip from the spindle center (workpiece center) is accorded with the infeed axis coordinate value of the wheel spindle stock at time of wheel dressing termination.