To provide a power supply system which prevents damages, such as fires when an abnormal temperature arises for generation of heat from an AC adapter.

The power supply system includes an AC adapter 100, having an AC/DC conversion means 101 which converts the AC voltage from a commercial power source into a DC voltage and outputs the DC voltage to an external electrical apparatus 200; a temperature detection means 104; an output control means 102, which designates a change of the DC voltage from the AC/DC conversion means based on a temperature detection signal from the temperature detection means; and a delay means 103, which delays the temperature detection signal outputted from the temperature detection means for a predetermined time and outputs a drive stop signal to the AC/DC conversion means; a voltage detection means 202, provided in the electrical apparatus, in order to detect a change of the DC voltage outputted from the AC/DC conversion means of the AC adapter; and a warning signal generation means 204 provided in the electric apparatus to generate a warning signal, based on the voltage detection means.