A power supply system includes an electric storage device, a connecting terminal area, a main energization line, a sub-energization line, a first energization switching unit for switching between an energized state and a non-energized state of an energization line of the main energization line connecting the electric storage device and a loading apparatus, a second energization switching unit for switching between an energized state and a non-energized state of an energization line of the main energization line connecting a branched part and the connecting terminal area, a third energization switching unit for switching between an energized state and a non-energized state of an energization line of the main energization line connecting the second energization switching unit and the connecting terminal area, and a control device that detects switching states of the first, second and third energization switching units and that controls their switching operations.