Disclosed herein is an optical waveguide comprising a core layer to be an optical waveguide region, an upper clad layer covering the core layer and a lower clad layer, characterized in that an ultraviolet control region for preventing ultraviolet light from entering is provided at any one location of under the lower clad layer, on an interface of the lower clad layer and the upper clad layer, and on the upper clad layer. And a method of fabricating this optical waveguide is also disclosed.