To cut a magnetic disk substrate at high precision.

Magnetic disk substrates S are held on rotary tables 18a, 18b, and cutters 16 serving as cutting tools for cutting the magnetic disk substrates S are fitted to the cutting wheels 17 of cutting heads 15a, 15b. The cutting resistance in the rotating direction, i.e., tangential resistance, applied to the cutters 16 is obtained by detecting the loads of table rotating motors 21, and the cutting resistance in the axial direction, i.e., normal resistance, applied to the cutters 16 is obtained by detecting the loads of wheel feed motors. The operation of the wheel feed motors applying the pressing force for the magnetic disk substrates S to the cutters 16 is controlled based on the tangential resistance or normal resistance. The cutters 16 and the rotary tables 18a, 18b are rotatively driven at the fixed rotating ratio respectively.