An optical waveguide includes a linear metallic thin film having a light delivering unit coupled to one end thereof, through which light is incident; and at least more than two dielectric layers surrounding the metallic thin film. In the optical waveguide, an effective refractive index and a propagation loss in the metallic thin film is reduced so that long-range light transmission is realized. Further, a loss of light caused by the coupling to optical fiber, which is coupled to one end of the metallic thin film, is simultaneously reduced.