Image forming apparatus provided with high voltage power source

An image forming apparatus includes a print engine which forms an image on a sheet; a high voltage power source substrate which applies output voltage to the print engine and which has a high voltage generating circuit for generating a high voltage by boosting inputted low voltage and a high voltage maintaining circuit for maintaining the high voltage at a predetermined value, the high voltage maintaining circuit being driven by the inputted low voltage; a low voltage power source which inputs the low voltage to the high voltage generating circuit and the high voltage maintaining circuit; and an ON/OFF circuit which switches whether or not the low voltage is inputted from the low voltage power source to the high voltage generating circuit and the high voltage maintaining circuit.