Some of the embodiments of this invention provide optical waveguides which achieve high use efficiency of core material and which are inexpensive. Some other embodiments of the invention provide methods of manufacturing such optical waveguides. An method of manufacturing an optical waveguide, according to the invention, comprises a step of forming a first clad by applying a resin on a substrate and curing the resin, a step of applying a core material between a recessed mold which has a recess having a shape identical to a shape of the core, and the first clad which is provided on the substrate, a step of curing the core material thus applied, thereby forming a core pattern having a shape corresponding to that of the recess, and a step of peeling the recessed mold from the core pattern and the first clad.