To obtain high efficiency at every operation points of a propeller by interlocking the pitch of an auxiliary propeller blades with the fluctuation of the pitch of main propeller blades pitch and fluctuating it larger than the fluctuation of the pitch of the main propeller blades.

Auxiliary propeller blades 2 adjacent to the rear edges of main propeller blades 1, having the diameter and the blade width smaller than those of the main propeller blades, and having the blade width radially decreased from the blade root to the blade tip are provided. Torsion of the main propeller blades 1 and the auxiliary propeller blades 2 is smaller than that of the normal propeller blades or zero. When the main propeller blades 1 are rotated on the axis parallel to the rotational surface of the propeller and the pitch is changed, the auxiliary propeller blades 2 are interlocked with the main propeller blades 1 and rotated, the rotation angle is made larger than the rotation angle of the main propeller blades 1. Therefore, the synthesized pitch distribution of the main propeller blades and the auxiliary propeller blades is made constant on all operation points, and high efficiency can be obtained.