PURPOSE: To reduce vibration of hull by employing H-shaped cross-section at the base of propeller vane while varying the pitch of propeller vane through torsion at the vane base section thereby suppressing variation of thrust and torque and occurrence of cavitation.

CONSTITUTION: The propeller vane 1 is formed such that the center of pressure CP is positioned further than the torsion central shaft CT while provided with the base section 2 having H-shaped cross-section. It is fixed to the boss section 3 rotatably in the arrow (a) direction. When the propeller vane 1 rotates in uneven stern flow, the attack angle against said flow will vary continuously during single rotation, but with correspondence to the increase of attack angle, the thrust will increase to increase the torsional torque in the direction for reducing the attack angle thereby the vane base section 2 having H-shaped cross-section will twist to maintain the attack angle of propeller vane 1 constant as the torsional torque increases thus to vary the pitch angle automatically in accordance to the direction of flow.