A power supply system includes: a first system having a first power supply; a second system having a second power supply; and an inter-system switch provided in a connection path connecting the first and second systems. First and second paths are provided in parallel between a connection point, at which the connection path is connected with the second system, and the second power supply. The power supply system further includes: a charging unit provided in the first path to charge, with the inter-system switch closed, a storage battery of the second power supply; a discharge restriction unit provided in the second path to restrict discharge of the storage battery; an abnormality determination unit that determines whether an abnormality has occurred in the discharge restriction unit; and a use restriction unit that restricts use of the second power supply upon determination that an abnormality has occurred in the discharge restriction unit.