Teaching (teach-in) work is performed, and from said teach-in position (SX), the workpiece (2) is ground by only a prescribed "trial grinding amount (A)." Subsequently, the diameter of the workpiece is measured. Based on the results of the measurement, the residual amount to be ground so that the workpiece has the finished dimensions (residual grinding amount) is calculated and grinding by only said "residual grinding amount (R)" is performed.