To provide a device which can change resistance of rotation to force, since a defect such as delaying an output rotating speed is caused in inverse proportion to strengthening ratio when strengthening force of output rotation by a method (a transmission) taken for changing a difference in a mutual rotating speed by using gears or the like, as a device for strengthening rotating force when a large load is applied to the rotating force.

If the rotating force can be amplified in response to a load (resistance) of rotation, a rotating speed can be maintained without increasing horsepower of prime mover. Thus, this rotational power amplifying device changes the force of the rotation to the resistance by a structure of surrounding the outside of a rotary shaft 1 of an equilateral pentagon having an angle of 72 degrees and being the same in the five sides, with an external receiver of an equilateral pentagon 2 having an angle of 72 degrees and being the same in the five sides.