POWER SUPPLY SYSTEM

A power supply system includes a plurality of sweep modules that is connected to a main line. Each sweep module includes a switching element that switches between connection and disconnection between a battery module and the main line and is formed of a MOSFET. A failure detecting device of the power supply system includes a temperature detecting unit configured to detect temperatures of the plurality of sweep modules and a failure determining unit configured to determine whether a difference between a temperature of one sweep module selected from the plurality of sweep modules and a reference temperature which is determined based on the temperatures of other sweep modules is greater than a predetermined threshold value.