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 thus serves as the upper clad layer; and characterized in that in the third step, a means for controlling the evaporation rate of the solvent in the solution containing the material for forming the second resin film is provided. The method permits the production of an optical waveguide device made of a resin, which is free of air bubbles at the branched portion of the waveguide device, the air bubbles being adversely affecting the transmission efficiency of the optical waveguide.