A washer that includes: an inner peripheral face formed in an arc shape; an outer peripheral face formed in an arc shape concentric with the inner peripheral face on a radially outer side of the inner peripheral face; and outer peripheral cut-out portions (such as a left outer peripheral cut-out portion and a right outer peripheral cut-out portion) formed at positions of the outer peripheral face corresponding to end portions (a first end portion and a second end portion) of the inner peripheral face to have the same shapes as outside shapes of the corresponding end portions of the inner peripheral face.