A battery module according to an embodiment includes a battery; a breaker that switches electrical connection of an output line from the battery to outside; a power source switch circuit that receives an internal source voltage supplied from the battery, an external source voltage supplied from an external power source, and an boot signal from outside, and switches a source of power that supplies source voltage from the external power source to the battery when at least one of the external source voltage and the boot signal is at a second level; and a control circuit that uses, as power supply, the source voltage that is output from the power source switch circuit, and controls operation of the breaker and of the power source switch circuit.