An optical element includes a substrate that transmits a light having a central wavelength in a wave range between 150 nm and 250 nm, and an n-layer antireflection film that is formed on the substrate, and includes, from the substrate, an n-2-th layer made of a high refractive index material, an n-1-th layer made of an amorphous material containing AlF.sub.3, and an n-th layer made of a low refractive index material, each of the high and low refractive index materials containing a crystalline material.