To reduce magnetic noise and vibration and reduce power loss at low revolution and at stationary while reducing the errors in estimation of a rotor position.

A high frequency voltage generator 202 adjusts the frequency of high frequency voltage Vh to be superposed on drive voltage and the frequency fc of PWM carrier, according to the drive frequency f detected by a drive frequency detector 201. Especially, in case that the frequency of drive voltage is low, it reduces the frequency of high frequency voltage, so it can reduce magnetic noise and vibration and also reduce power loss at low revolution and at stationary, while reducing the errors in estimation of a rotor position.