A thrust fan for a ship is provided to prevent cavitation generated in a rudder by allowing rotating stream generated by a screw to rectify by using a thrust fan. A thrust fan for a ship comprises an auxiliary thrust fan(40) installed in a rear stream of a screw to rotate in a direction opposite to the rotation direction of a screw(10). The auxiliary thrust fan(40) and the screw(10) are provided on the same rotating shaft(41) installed at the front end of a rubber. The auxiliary thrust fan(40) has a diameter corresponding to 30% to 50% of the diameter of the screw(10). The auxiliary thrust fan(40) has a plurality of rotation fans(42) protruding on the outer peripheral surface of the rotating shaft(41). The rotating shaft(41) has a cylindrical shape and an end inserted into the front end of the rubber. The rotation fans(42) operate by rear stream generated by the screw(10).
