A one-way clutch used in a wind power generation device integrally rotatably connects an input rotating body and an output rotating body to each other in a state in which a rotational speed of the input rotating body exceeds a rotational speed of the output rotating body, and breaks connection between the input rotating body and the output rotating body in a state in which the rotational speed of the input rotating body is lower than the rotational speed of the output rotating body. The input rotating body and the output rotating body are allowed to relatively move along an axial direction, and a maximum allowance of movement is set to be larger than variation of a distance along the axial direction between an input shaft and an output shaft caused by state change.