An optical fiber mounting waveguide device includes a substrate, an optical fiber mounting groove provided on a part of the substrate for mounting an optical fiber, an under cladding layer and a core sequentially formed on the substrate, and an over cladding layer formed on the core, the over cladding layer having an end surface facing to the optical fiber mounting groove, and wherein the core and the under cladding layer are protruded toward the optical fiber mounting groove with respect to the end surface of the over cladding layer.