Disclosed is a mirror unit and a method of producing the same. In one preferred form of the present invention, the mirror unit includes (i) a mirror with a multilayered film formed on a substrate, the multilayered film having two materials periodically laminated in layers on the substrate, and (ii) a substrate deforming device for producing deformation of a shape of the substrate of the mirror, wherein, in the multilayered film, the number of laminated layers in a predetermined region of the substrate differs from that in another region of the substrate. A mirror unit producing method according to another preferred from of the present invention includes (a) forming a multilayered film on a substrate, the multilayered film having two materials periodically laminated in layers on the substrate, (b) providing substrate deforming means in association with the substrate, the deforming means having a function for producing deformation of the shape of the substrate, and (c) partially removing the multilayered film.