PURPOSE: To obtain a simple cooler which can be repeatedly available by dissolving.separating water and compound through a separating membrane.

CONSTITUTION: The cooler comprises two vessels 1, 2, one 1 of which is filled with an elastic material 3 such as urethane containing water 5 and the other 2 of which is filled with compound 6 which is easily soluble in water and has high dissolving latent heat such as urea, etc. The vessels 1, 2 are connected by interposing a separating membrane 4 which passes the water but does not pass the compound therebetween. In the case of use, the vessel 1 is pressed to extrude the water contained in the material 3 to the vessel 2 side through the membrane 4 to dissolve it in the compound 6. The vessel 2 is rapidly cooled by latent heat at the time of dissolving the water in the compound 6. Since the collapsed material 3 tends to return to its original shape, the water in the vessel 2 is returned into the vessel 1 through the membrane 4. This is repeated to cool many times.