To provide a propulsion force generator utilizing a centrifugal force capable of eliminating the problems of a conventional generator utilizing the centrifugal force.

This propulsion force generator comprises a rotatably driving means, rotating shaft 10 rotated by the rotatably driving means, a mounting base panel 20 installed on the rotating shaft 10 and rotated together, a plurality of mass point elements 30 installed on the base panel 20 and rotated together, and a turning radius control guide body 40 for controlling the turning radius of the mass point elements 30. The mass point elements 30 are installed on the mounting base panel 20 with a phase difference equally provided in the turning direction, and allowed to move radially at each mounting position. A turning radius control guide body 40 guides the mass point elements 30 in contact therewith so that the turning radii of the mass point elements 30 become longer in a same direction around the rotating shaft 10 and shorter in an opposite direction.