The invention has an object to provide an optical device which can directly and efficiently introduce a planar incident light as it is and can efficiently obtain a planar total reflected light on a desirable interface without using a light guiding plate or an optical waveguide, and is constituted by a reflector having no absorption without depending on an incidence angle. The invention provides a planar optical device characterized by such a feature that when an incident light is introduced like a plane into the optical device, at least apart of the incident light thus introduced is totally reflected by an interface of layers constituting the optical device, while the incident light is not substantially emitted from an opposite side to an incident light introduction side.