PURPOSE: To equalize load distribution for a blade and improve its hydrodynamic characteristic, by arranging front and rear blades, in width narrower than width of a main blade, in an adjustable state of their angle, from the edge center of leading and trailing edge parts of the main blade to blade deflection parts.

CONSTITUTION: If a propeller blade A is rotated, water flows at the angle of incidence α for a pitch surface a-a. Angles of front and rear blades 2, 3 are adjusted in accordance with a change from a propeller advance constant J at this angle of incidence α. In this way, a value of load distribution of the propeller blade A is increased by cooperative action of the front and rear blades 2, 3 in area from the center of edge parts to blade deflection parts, and thrust can be increased as a whole unit of the blade A. Further negative pressure in a leading edge part of the blade A can be eliminated. In this way, equal distribution of a load and increase of a total load in the blade can be obtained to improve its hydrodynamic characteristic.