To provide a turbine fin in which the thrust efficiency of a propeller is improved by eliminating a lift loss at the tip of a turbine blade by changing a water flow at the tip of the turbine blade.

The turbine fin comprises a turbine hub having a center shaft of a propeller at the rear part of the propeller provided with a plurality of propeller blades and freely rotated with respect to the propeller, a plurality of turbine blades fixed to the turbine hub in a radial direction and a cylindrical duct fixed for connecting tips of the plurality of turbine blades to one another, wherein a sectional shape of the duct in parallel with the center line of a ship is a wing shape, a camber of the wing is directed toward the center shaft, a diameter of the turbine blade is set to about 24% to about 32% of a diameter of the turbine blade and a diameter of the duct at the bow side is set to be slightly larger than that at the stern side.