PURPOSE: To obtain continuous rotational movement, by automatically varying the weight balance acting on a disk by use of magnetic force.

CONSTITUTION: A disk 1 is rotatably set to a horizontal shaft 3 supported by a supporting base 2. On one side of the disk 1 hollow cylindrical bodies 4 and 5 are provided. The length of the hollow cylindrical bodies 4 and 5 is 1/2 of the radius of the disk 1. The hollow cylindrical bodies 4 and 5 face each other with the rotation center of the disk 1 therebetween and each of the cylindrical bodies 4 and 5 can posture horizontally at a position apart from the horizontal axis passing through the rotating center by 1/2 of the radius of the disk 1. At an end near the center of the hollow cylindrical bodies 4 and 5 superconductive ceramic plates 7 are installed. Permanent magnet spheres 6 are movably provided in the hollow cylindrical bodies 4 and 5. When the liquid nitrogen is injected from a liquid nitrogen injection nozzle 9 provided on the upper part, the superconductive ceramic plates 7 become superconductive and the permanent magnet spheres are repulsed and move to the outside diameter side, so that the balance of the moment are lost and the disk 1 will rotate.