An anti-reflection coating is formed on an optical surface of an optical member for reducing the amount of light rays reflected from the optical surface. For light rays in a wavelength range from 400 nm to 700 nm, the anti-reflection coating has a reflectance of 0.5% or less if the light rays are incident on the optical surface at angles within a range from 0 to 25 degrees, and it has a reflectance of 3.5% or less if the light rays are incident at angles within a range from above 25 degrees to 60 degrees.