A structure for effectively heating a battery. A battery is housed in a battery container. A condenser is formed such that a heating medium is in direct contact with a surface of the battery container, and condenses the heating medium to heat the battery via the battery container. The heating medium condensed by the condenser is supplied to an evaporator that heats and vaporizes the heating medium. The heating medium vaporized by the evaporator which is in vapor is circulated to the condenser.