PURPOSE: To obtain a multilayered film having high durability and superior resistance to mechanical friction by interposing an intermediate layer of a specified substance between each of SiO2 layers and each of TiO2 layers laminated on a substrate and by heating the resulting multilayered film to diffuse the substance of the intermediate layers in its adjacent SiO2 and TiO2 layers.

CONSTITUTION: SiO2 films 3, 5, 7 and TiO2 films 2, 4, 6 are laminated on the surface of a substrate 1 while interposing an intermediate layer of an intermediate substance such as Al2O3, MgO, ZrO2, CaO or Na2O between each of the films 3, 5, 7 and each of the films 2, 4, 6 by a physical film forming method. By heating the resulting multilayered film, the intermediate substance is diffused in its adjacent SiO2 and TiO2 films to form diffused layers 8. The concn. of the intermediate substance in each of the layers 8 is highest at the central part and is lowered toward the outsides. The thickness of the layers 8 is adjusted to about 30W100. The substrate is made of glass. The glass is heated during the heating of the multilayered film, and the glass is tempered by the heating and the following rapid cooling. A multilayered optical interference film having high durability and useful to increase or avoid reflection is obtd.