To reserve the heat of a battery for a long period without consuming the battery even after the operation of a heater is finished, by providing a heater, an insulation member, and a heat reserver, and arranging to suppress the heat radiation of the heat reserver to the outer surface side by the insulation member.

The heater of this battery heat reserving cover 1 is preferably made into an electric heater 3 which can continue to an external power source for charging of a battery equipped to a motor driving vehicle, or into an electric heater 3 connected to the generator of a vehicle to cut off the circuit when the engine is stopped. At the outer surface side of a flat heat reserver 5, an insulation member 4 consisting of a fire retarding material is provided, and as a result, the heat radiation to the outer surface side of the heat reserver 5 is suppressed. The heater 3 consists of a plastic compound body mixing a conductive filler, favorably, and it is made into a flat heating element having a self temperature control property. The heat reserver 5 is composed by filling a heat reserving material of an inorganic salt, to a soft bag. In this case, the heater 3 may be a warm water heater to lead in the warm water of an engine cooling system.