PURPOSE: To enable the heat reserving temperature within a heat reserving container to be set as required below the fusion point of a latent heat emission type heat reserving material, and thereby enable said heat reserving condition for a long time by providing each given caking means for each pack of heat reserving materials to which the latent heat emission type heat reserving material enabling super cooling is enclosed.

CONSTITUTION: In a heat reserving container 1 with a space section 1a having an object to be kept warm, the inside of the bottom plate 2a of a container main body 2 composed of insulating materials is formed with a hollow section 3, and plural numbers of packs 6 of heat reserving materials are arranged in the hollow section 3, which is formed in such a way that a latent heat emission type heat reserving material 4 is enclosed by means of aluminum laminate sheets 5. In a temperature sensing actuator 9, one portion of it is a spring made of a shape memory alloy so that it is changed in shaped at a temperature set as required. This thereby permits the aforesaid striking section 10b to strike the aforesaid spring 7 in a coil form located down below by means of the energizing force of a spring 10c in a coil form. Then, this permits sliding frictional force to be imparted to the latent heat emission type heat reserving material 4 which is in a super cooling condition at a fusion point of 58°C so as to let the latent heat emission type heat reserving material 4 to cake so that latent heat is released.