To obtain window glass having high transmittance of light which prevents reflection of light with a wide incident angle by forming a multilayered antireflection film on the surface to have specified or higher transmittance of light entering at a specified incident angle.

This glass is window glass 1 for an optical semiconductor which covers the window hole 3a of an optical semiconductor package 3, and the glass has a multilayered antireflection film 2 on its surface. The glass transmits light incident at 0 to 50 incident angel by ≥90% transmittance. As for the material of the antireflection film, for example, TiO2, MgF2, Al2O3, ZrO2 and Ta2O5 can be used for high refractive index layers, and for example, SiO2 and TiO2 can be used for low refractive index layers. As for the combination of these, for example, combination of TiO2 and SiO2, or MgF2 and SiO2 can be used. The high refractive index material and the low refractive index material are alternately deposited to form the multilayered film, and the obtd. multilayered film is applied on both surfaces of the window glass 1 for the semiconductor to obtain the antireflection film 2. Preferably, the multilayered film is formed to have at least 4 layers on one surface and 8 or more layers on both surfaces.