Disclosed herein is an optical waveguide comprising a core layer to be an optical transmission region, an upper clad layer and a lower clad layer covering the core layer, in which the core layer, the upper clad layer and the lower clad layer are formed from resin materials, characterized in that a microlens made of a material having a higher refractive index than that of a material constituting said core layer is disposed in the vicinity of an end face of said core layer.