A power supply system for a vehicle includes: a high-voltage battery; a first power supply arrangement; a second power supply arrangement; and a third power supply arrangement, wherein the first power supply arrangement is connected to a first load including at least an autonomous driving system and includes a first DC-DC converter, a first battery, and a connection control unit, the connection control unit being configured to control a connection state between the first DC-DC converter and the autonomous driving system and a connection state between the first battery and the autonomous driving system.