PURPOSE: To provide a power supply device which outputs a voltage having a low voltage and the little ripple of an AC power supply from a step-down chopper, and the high frequency output voltage applied to the load of an inverter of which also has the little ripple of the AC power supply.

CONSTITUTION: As an applied voltage to an inverter 2 is applied to either of switching elements Q1, Q2 which is off, when the voltage of a main AC power supply Vs is smaller than the voltage of a condenser C2, the voltage of a condenser C1 is applied when both switching elements Q1, Q2 are off. When the voltage of the main AC power supply Vs is larger than the voltage of the condenser C2, the added voltage of the voltage of the main AC power supply Vs and the voltage of the condenser C1 is applied to the switching element Q1, and the voltage of the condenser C1 is applied to the switching element Q2.