An outer casing includes a housing configured to house a battery, a gas adsorbing unit disposed outside the housing and including an adsorbent that can adsorb a first gas generated inside the housing, and a first valve configured to discharge the first gas from the gas adsorbing unit to outside of the outer casing. The first valve may be connected to the gas adsorbing unit. A battery module includes the outer casing and a battery disposed in the housing of the outer casing.