In a power supply system, a first system includes a first power supply connected to a first load. A second system includes a second power supply connected to a second load. A connection path connects the systems. An intersystem switch is provided on the connection path. A control apparatus sets the intersystem switch to a closed state and sets a voltage of the first power supply to be higher than a voltage of the second power supply to be a first state in which power supply is performed from the first power supply to the loads. In response to a reverse-direction current from the second system to the first system flowing to the connection path in the first state, the control apparatus sets the intersystem switch to an open state to be a second state in which power supply is performed from the second power supply to the second load.