A power supply system includes a power source, a relay, a switch, and a controller. The relay is interposed between the power source and a load. The switch is configured to be coupled to the load in a state where the switch allows or disallows for power supply from the power source to the load when the relay is in a closed state. The controller is configured to control an operation of the switch. The controller is configured to execute forced driving control at a time of a closing operation of the relay. The forced driving control causes the switch to operate independently of a request for driving the load and thereby causes power to be supplied from the power source to the load.