A one-way clutch includes: an inner ring provided with an inserting opening for permitting insertion of a rotation shaft and rotatable integrally with the rotation shaft by being engaged with the rotation shaft; an outer ring engaged with an outer peripheral surface of the inner ring and rotatable in one direction relative to the inner ring and non-rotatable in a direction opposite to the one direction; and an elastic metal plate member, engaged with the inner ring, for limiting movement of the inner ring relative to the outer ring in a rotational axis direction of the outer ring. When the rotation shaft is mounted in the inner ring, the elastic metal plate member includes a leaf spring portion positioned and elastically deformable in a gap between the rotation shaft and the inner ring.