An antireflection coating provided on an optical element which passes through at least two wavelengths of light in the wavelength range of 1300-1600 nm, wherein the antireflection coating comprises: a high refractive index layer; a low refractive index layer having a refractive index lower than a refractive index of the high refractive index layer; and a supplementary layer having a composition different from a composition of the high refractive index layer or from a composition of the low refractive index layer, and being provided adjacent to the high refractive index layer or to the low refractive index layer.