NOVELTY - The temperature adjustment mechanism has a battery pack (10); and a PTC heater (20) that is provided between and in contact with the battery pack and a vehicle main body (30). The PTC heater is in contact with an entire surface of the battery pack that faces the vehicle main body.    USE - Temperature adjustment mechanism for vehicle (claimed), such as fuel cell vehicle, and electric motor vehicle.    ADVANTAGE - The temperature adjustment mechanism is capable of restraining excessive temperature rise or excessive temperature drop of an electric power supply body. The excessive cooling of the battery pack is restrained by causing the PTC heater to generate heat, even when the vehicle main body is excessively cooled. The PTC heater is not heated, and the heat generated by the battery assembly is mostly transferred to the vehicle main body via the PTC heater, therefore, the temperature rise of the battery assembly can be restrained, and the degradation of the electric cell characteristic associated with the temperature rise can be restrained. The rate of the heat transfer via the PTC heater drops, and therefore the transfer of heat from the vehicle main body to the battery pack less easily occurs. The temperature rise of the battery pack can be restrained by restraining the heat that the battery pack receives from the vehicle main body, and the degradation of the electric cell characteristic of the battery assembly can be restrained. If the temperature of the battery pack is zero degrees Celsius or negative 30 degrees Celsius, the PTC heater is electrified, and the battery pack is warmed by the generation of heat of the PTC heater; therefore, it is possible to restrain the excessive cooling of the battery pack or the battery assembly and therefore restrain the deterioration of the electric cell characteristic.    DESCRIPTION OF DRAWING(S) - The drawing shows the schematic sectional view of a temperature adjustment mechanism.    Battery pack (10)    Battery case (11)    Battery assembly (12)    PTC heater (20)    Vehicle main body (30)