PURPOSE: To obtain a reflecting mirror which has reflecting surfaces protected and an improved reflection factor and is suitable to a rotating polygon mirror, etc., by forming an SiO2 film and a TiO2 film over a specularly finished base material in order.

CONSTITUTION: The blank 1 of the rotating polygon mirror which has small polygonal planes 1a is specularly finished by, for example, corrosion resisting Al alloy and then an Al film 2 is formed on each plane 1a to about 1,000. Then, the SiO2 film 3 and the TiO2 film 4 are formed in order to optical film thickness nd and λ0/4 (where (n) is a refractive index, (d) is geometric thickness, and λ0 is in-use wavelength). The Al film 2 may be omitted depending on the state and kind of the base material 1. Thus, a reflection factor higher than that of the cut mirror surface is obtained, the mirror surfaces are protected, and a decrease in reflection factor due to oxidation is prevented, obtaining the reflecting mirror suitable to obtain a galvanomirror, etc., for the optical deflector of, specially, a laser printer, etc.