PURPOSE: To prevent the exfoliation of an SiO film and Al film forming a metallic mirror by forming an Ni film on an Al substrate then laminating and forming successively the Al film and protective film via a Cr film thereon.

CONSTITUTION: The Ni film 12 is formed to about 50μ thickness by an electroplating method, etc. onto the Al substrate 11 and thereafter the surface is finished to a specular surface by polishing. The Cr film 13 is deposited and formed to 100W300 by a vapor deposition method onto the substrate 11. The Al film 14 is deposited and formed to about 2,000 thickness by vapor deposition thereon and further the SiO film 15 as a surface protective film is deposited and formed to about 1,000 thickness on said film to manufacture the metallic mirror. The Cr film having the high deposition strength to both metallic films of the Ni film and Al film is thus formed between the Ni film and the Al film and the Al film is formed on the Ni film in the form of sandwiching the Cr film and therefore such an accident as the exfoliation of the Al film formed on the Ni film during the use of the metallic mirror is obviated.