PURPOSE: To manufacture fresh water from sea water by utilizing the solar heat, a natural energy while simultaneously with pumping up the sea water.

CONSTITUTION: Sea water 3 is introduced from the sea water area 1 into a water tank 2 communicating with a sea water area 1. The temperature of air introduced in a dome 5 of a film structure with which a space above the water tank 2 is closed is increased by solar heat during the daytime to generate steam from a sea water surface in the water tank 2. Air in the dome 5 heated during the daytime is discharged to the outside of the dome 5 and cold air is introduced in the dome 5 to promote the generation of dew. Dew dripping from the inner surface of the dome 5 is received by a water introduction film 8 stretched from the center of the dome 5 toward the bottom of the dome 5 to collect water.