Abstract: There is provided an evaporative desalination apparatus of sea water using a phase change medium, and more particularly, a desalination method by evaporation, for producing fresh water from sea water by using various high heat sources, such as solar heat, engine heat and the like. Instead of a conventional method in which warm water is supplied to an evaporator of an desalination apparatus to evaporate seawater, the present invention provides the phase change medium capable of supplying a much more amount of heat to the evaporator, thereby enhancing the efficiency of the desalination apparatus to produce a great quantity of fresh water or manufacturing a compact desalination apparatus. The method of providing the amount of heat according to the present invention is to circulate the phase change medium. In the present invention, the latent heat generated when a gas of high heat is injected and is phase-changed to a liquid state is used to evaporate sea water.