An optical waveguide substrate 1 includes an optical waveguide 9 composed of a multi-layered film 4 of a plurality of optical material films 5, 6 and having end faces onto which a light is made incident or from which the light is emitted. The end face is an etched surface, and it is provided, on the end face, an unevenness 7 corresponding to a difference of etching rates of the optical material films.