To provide a reflection preventing film indicating reflection preventing effect in a wide range of light incidence angle in light selected from the wavelength range of 120 to 300 nm, in particular, in light having a specific wavelength (incident angle characteristic is satisfactory), having low average reflection rate over the entire incidence angle, and having small fluctuation of polarized light reflection rate for changes of incidence angle of light (separation of polarized light component is small).

This reflection preventing film is provided with a high refractive index substance layer having optical film thickness of about 0.47λ0, a low refractive index substance layer having optical film thickness of about 0.42λ0, a high refractive index substance layer having optical film thickness of about 0.27λ0, and a low refractive index substance layer having optical film thickness of 0.24λ0 like stacked layers in order starting from a substrate side on a substrate through which light for preventing reflection penetrates using a design reference wavelength in the vicinity of wavelength of the light as λ0.