An optical element for reflecting solar light has excellent weather resistance, and furthermore, a high reflectance in a wide band. When solar light enters an optical element (OE), light (L1) in a short wavelength band among the solar light is reflected by a dielectric multilayer film (DF). Other light (L2) in longer wavelength bands are passed through the dielectric multilayer film (DF), then a base material (SS), and reflected by a metal deposition film (MV) to pass through the base material (SS) and the dielectric multilayer film (DF). Thus, high reflectance in a wide band is ensured.