PURPOSE: To obtain an inverter in which vibration and noise are suppressed.

CONSTITUTION: A control circuit feeds a motor 3 with output power from an inverter while fixing the operating frequency constant and varying the modulation frequency sequentially from 0 to 10kHz. When output signal from any one of vibration sensors 5, 5 exceeds a predetermined level, detection frequency at that time is stored. The motor 3 is then driven with operating frequency being increased sequentially and modulation frequency is also increased thus performing PWM control. Power subjected to PWM control is then fed from an inverter main circuit 1 to the motor 3 and the motor 3 is controlled such that the modulation frequency region is skipped.