To provide an optical wave guide that may be produced by reproduction method in easy and simple manner, and has a structure that prevents light signal in its inside from leaking out from core, and a method for producing the same optical wave guide. A concave slot for forming a core is formed on the upper surface of a cladding substrate. And on both sides of the concave slot, cavities are formed via flat portions. An ultraviolet ray hardening type transparent resin is applied onto the surface of the cladding substrate, thereafter the transparent resin is pressed by a stamper. At this moment, a core is formed in the concave slot and excessive transparent resin is pressed between the stamper and the flat portions flows into cavities, as a result, it is possible to make the transparent resin thin in a short time. Thereby, it is possible to make the transparent resin left on the flat portions into thickness and width enough to prevent light in the core from leaking out.