The transmission member moves in a longitudinal direction of the input member to adjust a line b connecting an input central line (A) to an output central line (B) of the output shaft and a line a connecting a rotating central line (C) of the rotation shaft to the output central line (B) of the output shaft so that the lines a and b have the same length or lengths different from each other, thereby changing the rotational force of the input member to transmit the changed rotational force to the output member or transmitting the rotational force to the output member as it is.