PURPOSE: To prevent the irregularity of rotation by controlling an energized current by torque variation correction data so that generated torque is constant.

CONSTITUTION: A controlling means of a brushless DC motor 8 is constituted of a microcomputer 1, a microcomputer 2, a ROM 3 and a RAM 4, and has a command generation circuit 5, a driving interface circuit 6, a driving circuit 7 and a detection interface circuit 10. The command generation circuit 5 outputs a state command signal of the motor 8, and generates a speed command signal and the like. The driving circuit 7 operates on a control signal (pulse-like signal), and rotates the motor 8 at a required speed. At that time, the ROM 3 is a means to store torque variation correction data as well as a program of control operation, and the current is controlled by the torque variation correction data so that generated torque is constant. Accordingly, the correction data is calculated by the microcomputer 1, and the irregularity of speed can be reduced by converting the correction data into the pulse-like signal of the driving circuit 7.