BATTERY MODULE

Battery module includes: a battery stack in which a plurality of batteries provided with a valve that ejects gas are stacked in a first direction; a discharge path that discharges gas ejected from the valve in a second direction intersecting the first direction; light emitter that is provided on one end in the first direction of the battery stack and emits light to the discharge path; and light receiver that is provided on another end in the first direction of the battery stack and receives the light emitted from light emitter.