To provide a rotary speed-up device, which can realize increase in revolutions by magnets by a method where magnets fixed to a rotary plate and magnets fixed to a fixed plate are provided respectively and repulsion forces between both the magnets, which are braking forces, when both the magnets come closer to each other are suppressed and the repulsion forces between both the magnets are applied effectively only in the rotation direction.

A rotary plate 14, fixed to a rotary shaft 4 so as to rotate integrally with it, is made to face a fixed plate 15. A plurality of vertical magnets 16, arranged radially with certain intervals, demagnetizing magnets 17 placed on the one side surfaces of the tips of the vertical magnets 16 and plate magnets 18 placed between the adjacent vertical magnets 16, are provided on the facing surfaces of the rotary plate 14 and the fixed plate 15. The rotary plate 14 and the fixed plate 15 are made to face each other, so as to have a rotation gap between the respective tip surfaces of the demagnetizing magnets 17 on both the plates 14 and 15 and have the polarities of the facing tips of the vertical magnets 16, on both the plates 14 and 15 equal to each other. Furthermore, the number of the vertical magnets 16 on the rotary plate 14 and the number of the vertical magnets 16 on the fixed plate 15 are different. Repulsion forces produced by magnetic lines of forces of both the vertical magnets 16 and 16 are applied effectively in the rotating direction only to increase the speed of the rotary shaft 4.