In a link of the present invention, a support body and a valve body are connected in a first arrangement in which a first link-forming member is supported by the support body in a rotatably movable manner and a second link-forming member is supported by the valve body in a rotatably movable manner. In the link, a link length that is the length of the first link-forming member and is the distance between a rotation axis with respect to the support body and a rotation axis with respect to the second link-forming member is different from a link length that is the length of the second link-forming member and is the distance between a rotation axis with respect to the valve body and a rotation axis with respect to the first link-forming member. Furthermore, the shape of the link enables connection between the support body and the valve body even in a second arrangement that is the reverse of the first arrangement.