The diameter, the orientation flat width/notch depth and the length of the block 10p are measured by the measuring devices 71a, 71b and 71c respectively and then the machining errors .DELTA.Dp, .DELTA.Wp and .DELTA.Lp in the measured values against the set values are calculated at the error calculation unit 833. Then .DELTA.Dp, .DELTA.Wp and .DELTA.Lp are stored in memory at the memory unit 834 in correspondence with the identification codes IDi and IDj of the grinding device 5i (i=1-N) and the cutting device 6j (j=1-M) that performed the machining. Then at the average value calculation unit 835, the average values of .DELTA.Dp and .DELTA.Wp for each of the grinding devices 51-5N and the average value of the .DELTA.Lp for each of the cutting devices 61-6M are calculated. The average values of .DELTA.Dp and .DELTA.Wp are supplied to the corresponding grinding device 5i as the diameter correction value and the width/depth correction value respectively and the average value of .DELTA.Lp is sent to the corresponding cutting device 6j as the length correction value from the transmission unit 836.