Abstract: A method for the preparation of an optical waveguide device characterized in that it comprises a first step for forming a first resin film on a substrate provided thereon with a lower clad layer; a second step for patterning the first resin film into a shape of an optical waveguide to thus form a core layer; a third step for forming a second resin film by coating the surfaces of the lower clad layer and the core layer with a solution containing a material for forming the second resin film according to the spin-coating method in such a manner that the thickness of the resulting film as measured from the upper surface of the lower clad layer and as determined after drying ranges from 3 to 10 times the thickness of the core layer and then drying the coated layer; and a fourth step for removing the second resin film in such a manner that the thickness of the second resin film as determined from the upper surface of the lower clad layer is less than 3 times that of the core layer and that the second resin film thu

Abstract: The present invention provides an optical device which has only a small number of ruptures on the edges of the surface and back face of the substrate as well as a method for the preparation of the same.