In a power supply system, a voltage monitor detects a voltage of output power output from a DC/DC converter. A step-down unit steps down the voltage of the output power and supplies the output power to a load. A distributor control unit controls the step-down unit based on the voltage detected by the voltage monitor. In a power satisfaction state in which the voltage detected by the voltage monitor is equal to or higher than a predetermined threshold voltage, the distributor control unit controls the step-down unit to step down the voltage of the output power and supply the output power to the load. In a power shortage state in which the voltage detected by the voltage monitor is less than the threshold voltage, the distributor control unit controls the step-down unit to supply the output power to the load without stepping down the voltage of the output power.