Abstract: A propeller in particular for a ship has blades each of which is pivotally arranged in the hub of the propeller so that the blade is capable of pivoting to and fro in an axial plane between forward and rearward positions. The blades are constructed such that each of the blade profiles formed as the intersecting face between a cylinder face coaxial with a propeller and a blade, is symmetrical in a position between forward and rearward positions which are determined by fixed stops in the hub and/or the simultaneous actions of the centrifugal force and the hydrodynamic pressure on the blade at a predetermined speed of rotation. This imparts a high efficiency and a quiet and steady operation to the propeller, when the ship navigates forwardly and rearwardly.