To provide an optical element showing an excellent reflection characteristic over a long period in use under an extreme ultraviolet ray.

A lower layer 31 functioning as a diffusion prevention layer is provided between an oxidation-resistant metal in an upper layer 32 and the surface layer of a multilayered film 20. The lower layer 31 includes MoSi2 as a main component, and prevents effectively the oxidation-resistant metal such as ruthenium, rhodium, platinum or gold constituting the upper layer 32 from diffusing into the multilayered film 20 surface layer, by MoSi2 functioning as a dense prevention layer. The lower layer 31 including MoSi2 as a main component also has a function for preventing moisture or oxygen passing the upper layer 32 from invading the multilayered film 20, and is excellent from the viewpoint of oxidation resistance. Namely, the lower layer 31 can prevent more surely the moisture or oxygen from invading the multilayered film 20 in cooperation with the upper layer 32, while suppressing deterioration of the reflection characteristic.