PURPOSE: To provide a multilayer film reflecting mirror excellent in moisture resistance and heat resistance, and suitable for any kind of application of a light source.

CONSTITUTION: After laminating titanium oxide and strontium fluoride alternately on a reflecting base 1 having a concave 2, a multilayer film 4 is formed by firing treatment at 300°C or higher. Thereby, the multilayer film 4 excellent in moisture resistance and heat resistance is formed so as to suit a light source having higher output and longer life sufficiently, and to be applicable to the reflecting mirror of all kinds of light sources regardless of the applications of the light sources.