To provide a control device for a compressor motor, suppressing the rotating vibration of the compressor even when an error occurs in a compression starting position.

The control device for the compressor motor controls the driving voltage of a motor by multiplying an average voltage command corresponding to a deviation in the rotating number of the motor 3 for driving the compressor by a torque control pattern changing corresponding to a change pattern of loading torque during one rotation of the motor. It comprises a compression starting position detection part 11 for detecting the compression starting position of the compressor, a rotating number variation detection part 20 for detecting the variation of the rotating number of the motor, correction parts 21, 22 for correcting the detected compression starting position in accordance with the detected variation of the rotating number, and a torque control pattern storage part 12 storing the torque control patterns. The driving voltage of the motor is controlled by multiplying the average voltage command by the torque control pattern read out of the torque control pattern storage part at a timing for the compression starting position corrected by the correction part.