To provide a vibration alleviating apparatus for an air conditioner for reducing vibrations, by a repetition of a regenerative state and a power state of an induction motor of the conditioner to be driven by an inverter.

In an inverter 3, the variation in energy communicated between a DC power source 7 and a power converter 8 is detected as a voltage change by a voltage change detector 9. Only the change content of the voltage change is extracted from an AC component by a change content detector 10 is waveform shaped into a pulse. The pulse is outputted. A waveform calculator 11 calculates a regenerative frequency change amount and a power frequency change amount based on pulse widths of the pulses, corresponding to the regenerative state and the power state. Thus, a fundamental frequency command value for designating the frequency of the converter 8 and a boosted chopper reference voltage command value for designating an output voltage of a booster chopper 6 are corrected, based on the regenerative frequency change value when regenerating or based on the power frequency change amount at the time of the power state, thereby controlling the direction for suppressing vibration.