PURPOSE: To provide a stable heating source of low temperature by a method wherein as a temperature of member to which a heating source of low temperature is supplied is increased more than a predetermined temperature, a controlling device is obtained, a mixing agent is flowed from a plurality of storing chambers into each of mixing chambers, several mixing agents are mixed to each other within the mixing chamber so as to generate endothermic reaction.

CONSTITUTION: As a temperature of a cold plate 3 is increased more than a predetermined value and this increased temperature is detected by a temperature sensor 5, a controlling device 1 is operated and valves 6a and 6b are opened and then a mixing agent if supplied from a plurality of storing chambers 4a and 4b into a mixing chamber 2. An endothermic reaction is generated through a mixing of a plurality of mixing agents so as to decreased a temperature of a thermal accumulation unit 7 and a cold plate 3. Accordingly, an arrangement of the thermal accumulator 7 enables a thermal capacity to be increased, resulting in that even if a large amount of heat is generated within a short period of time at the cold plate 3, this is processed and then the cold plate 3 can be kept always at a stable temperature.