When it has been determined according to a voltage detected by a voltage detecting unit 31 that a voltage detection line 23 between a focused-on battery 21 and the voltage detecting unit 31 has been broken, operations of each of switches 22 are controlled to separate a battery module 2 that includes the voltage detection line 23 from a power supply apparatus 1. When it has been determined according to the voltage detected by the voltage detecting unit 31 that the focused-on battery 21 has been overcharged or overdischarged, power input to, or output from, every battery module 2 is limited.