To increase precision in straightness on a journal thrust surface relative to an outer peripheral surface of a journal in a crankshaft, a control system is provided for controlling movement of a cutter in axial directions by running a control program transferred from an automatic programming apparatus. The automatic programming apparatus corrects machining data on the basis of data for correcting the straightness gained through a comparison between results of a measurement of machining dimensions of the journal thrust surface in the workpiece on which a cutting process has been carried out and target machining dimensions for the journal thrust surface. A control program is prepared on the basis of the corrected machining data after correction of the machining data.