PURPOSE: To provide a method for switching between speed control and torque control without causing any shock in the rotation of a motor.

CONSTITUTION: A function generating function 17 for interpolating the values of a speed signal and a speed command signal of a motor being inputted at the switching timing from torque control to speed control is provided on the output side of a speed setter 10a and a torque control value being outputted at that timing is set in the integrating function of an automatic speed regulating function 181. A function generating function 11 for interpolating the values of motor current signal and torque command signal being inputted at the switching timing from speed control to torque control is provided on the output side of a torque setter 10b. When an automatic speed regulating function equipped with no integrating function is employed, predetermined operation results and a speed command signal are interpolated.