In an AC power supply apparatus, first and second switching circuits connected in series to an input terminal to which a DC input power supply is connected include first and second rectification elements, respectively. A capacitor, an inductor, and a capacitive load are equivalently connected in series to the second switching circuit. The capacitor is charged after the first switching circuit is turned on before the second rectification element is turned off and the charged capacitor is caused to discharge after the second switching circuit is turned on before the second rectification element is turned off. The above operations are periodically repeated. The voltage of the capacitive load is reversed with current flowing during the charge and the discharge of the capacitor to adjust the on and off periods of the first and second switching circuits in order to supply desired AC voltage to the capacitive load.