PURPOSE: To obtain the title apparatus capable of producing fresh water with high thermal efficiency at a low cost by reheating sea water, used for cooling in a condensation chamber, with a heat pump system refrigerator combined with a desalting drum having an evaporation chamber and the condensation chamber and by boiling the reheated water in the evaporation chamber.

CONSTITUTION: Absorption type heat pump system refrigerator 1 consisting of generator 2, condenser 3, evaporator 4, absorber 5, etc. is combined with desalting drum 6 having evaporation chamber 7 and steam condensation chamber 8. As the driving heat source of refrigerator 1 solar heat collector 10 heating a heat medium being circulated with pump 9 and hot water heater 11 supplying heat are used. Heat source 12 such as waste heat giving hot water of above 100°C may be used. As the heating source of refrigerator 1 sea water fed from sea 14 with pump 13 is used. Sea water is passed through cooler 16 with pump 15, heated with refrigerator 1, and flashed to evaporate the water. The resulting steam enters chamber 8, where it is cooled with sea water flowing through cooler 16, and converted into fresh water 17.