To provide a sea water desalination apparatus capable of satisfactorily eliminating turbid components in seawater and suppressing a decrease in filtration efficiency with time in a filtration means even when simplifying a pretreatment means, and further, simplifying and miniaturizing the apparatus and preventing the deterioration of a reverse osmosis membrane by using a prescribed pressurizing means.

This seawater desalination apparatus is provided with the filtration means for filtering the seawater which is taken in, a pressurizing means for pressurizing and feeding the seawater filtered by the filtration means, and a reverse osmosis membrane treatment means for treating the seawater pressurized by the pressurizing means by means of a reverse osmosis membrane method. As the pressurizing means, an inverter capable of controlling a magnetic flux vector is used as a motor for a pump, and one plunger pump capable of pressure feed while keeping the basic torque of the motor from the 1/20 to 1.5 times of a rotating speed is used.