The invention relates to a method for producing a polymeric optical waveguide-forming master plate, comprising: laying a thread which does not transmit rays used for subsequent exposure on a substrate for a master plate, applying a positive resist material onto the substrate to have a thickness such that, when parallel rays are vertically radiated onto the resist from a side opposite to a substrate side with respect to the thread and then the resist is developed, a layer made of the resist is formed at whole space where the rays have not been radiated; radiating parallel rays substantially vertically to the substrate to expose the resist to the rays; and developing the exposed resist on the substrate to form a convex portion corresponding to a shape of an optical waveguide core, to waveguide production methods using the same, and to the resultant waveguide.