The utility model discloses a sea water desalinating device comprising a sea water tank, a condensing device and a fresh water tank. The sea water tank is connected with the condensing device through a steam pipeline and then is communicated with the fresh water tank; and the condensing device is a film falling type condenser, and comprises a shell as well as a water distribution device, a heat conduction device and a water collection plate which are arranged in the shell. The sea water desalinating device provided by the utility model utilizes the film falling type condenser to overcome the technical problem that the condensing device in the prior art has poor effects. The film falling type condenser can be used for feeding sea water, pre-heating and degassing, so that the condensing heat exchange efficiency of an evaporator can be improved; the corrosion on equipment is reduced; and the water making cost is reduced.