To provide a rotation power intensifier capable of increasing power of an output rotation while rotating an input rotation and output rotation at the same speed.

An input rotation transmission member 4 and an output rotation transmission member 6 rotatably arranged in parallel are mutually connected with two expansion rods 8, 9 arranged with a shifting phase by 180° at both sides thereof. The distance of the pivot point of each expansion rod 8, 9 from the axial center of the input rotation transmission member 4 in the radius direction and the distance of the pivot point of each expansion rod 8, 9 from the axial center of the output rotation transmission member 6 are set same. The first expansion rod 8 transmits the rotation of the input rotation transmission member 4 to the output rotation transmission member 6 in a range of 0 to 180°, and the second expansion rod 9 transmits the rotation of the input rotation transmission member 4 to the output rotation transmission member 6 in a range of 180 to 360°. The rotation of the input rotation transmission member 4 can be transmitted to the output rotation transmission member 6 with increased power at the same speed by changes of angles of the expansion rods 8, 9 to the input rotation transmission member 4 and the output rotation transmission member 6.