A tank main body accommodates a heat exchanger including a heating medium pipe. A plurality of heat exchanger fins are coupled to the heating medium pipe to divide the interior of the tank main body into a plurality of spaces. A hydrogen storage alloy is provided in the spaces. An absorption portion is provided in the spaces. The absorption portion is deformed by a force generated by expansion of the hydrogen storage alloy, thereby absorbing the force. Therefore, the heat exchanger is prevented from being deformed or damaged even if the bulk density of the hydrogen storage alloy is reduced due to expansion and pulverization of the hydrogen storage alloy.