To solve a problem such that body weight is not efficiently linked with rotational force because a gravity direction is at a substantially right angle with a rotating direction at the moment when the position of a pedal reaches a maximum point and the just before/just after and at the moment when the position reaches a minimum point and the just before/just after when pedaling a bicycle, and achieve a state that the one pedal already passes the maximum point is obtained when the other pedal is depressed up to the mini mum point.

Left and right cranks and a bearing of a chain ring are separated from each other. An elliptical slide gear having two slits across a center is fixed by a slide gear bearing and is rotated by left and right hooks integrated into each of the left and right cranks. The rotary shafts of the left and right hooks are the same and are made parallel to a rotary shaft of the chain ring. The hooks rotate the chain ring, sliding in the slits of the slide gear.