PURPOSE: To improve reflectivity and durability by providing a high reflectivity film of specific thickness on a substrate and providing alternately ≥1 sets of a low reflective index film and high reflective index film each set consisting of the two layers thereof on said film.

CONSTITUTION: A high reflective film 2 having ≥250 thickness, for example, Al film is provided on a substrate and ≥1 sets of a low reflactive index film 3, for example, MgF2 film and a high refractive index film 4, for example, LaF3 dilm, each set consisting of the two layers thereof are disposed alternately thereon. The thicknesses of the film 3 and the film 4 are made optically odd-fold λ/4 including the phase correcting component at the boundary face with the film 2 if the wavelength to the used is λ. The film thickness of either one of the alternate layers 3, 4 is further made 3/4λ including the phase correcting component and the layers 3, 4 are provided preferably in one or two sets. The reflectivity is indecreased by providing the layers 3, 4 in such a way and good durability is obtd. by forming one of the films to 3/4λ. The mirror is used for producing ICs.