To provide a charger reducing power consumption in a standby state where a battery is not being charged.

An input terminal T2 of a switching circuit 4 connects a capacitor Cz via a resistor R2, and connects the capacitor Cz to between a collector and an emitter of a phototransistor 9b of a second photocoupler 9. When the intermittent supply of a primary DC voltage is stopped and an output voltage Vn becomes less than a predetermined voltage and the phototransistor 9b of the second photocoupler 9 is turned off, a terminal voltage Vx of the input terminal T2 is increased up to a threshold while gradually requiring a time at a time constant determined by the capacity of the capacitor Cz and a resistance value of the resistor R2. The resume of intermittent supply of primary DC voltage to an output transformer TR is delayed, and the power consumption is reduced.