PURPOSE: To generate a large thrust by a small turning force by turning a permanent magnet within a plurality of circular iron pieces arranged in an annular shape and by successively opening and shutting two up and down moving planar iron pieces fitted to the outside of said circular iron pieces.

CONSTITUTION: A plurality of circular iron pieces 1 are arranged in an annular shape and a permanent magnet 4 turning around a rotating shaft 5 is provided within said circular iron pieces. Outside said circular iron pieces 1, up and down movable planar iron pieces 2, 3 are arranged relative to each circular iron piece 1. Said planar iron pieces 2, 3 corresponding to magnetic poles N, S of the permanent magnet 4 are opened up and down. when the permanent magnet 4 is turned, the corresponding planar iron pieces 2, 3 are opened and shut accordingly. When output is made larger, a plurality of apparatus are fitted in the direction of said rotating shaft of the permanent magnet in such manner that their setting angles deviate from each other. Thus, a large biasing force can be generated by a small turning force.