Optical fiber guides are provided outside a waveguide mounting region of a supporting substrate. Optical fibers are provided so as to be fitted in the optical fibers, respectively. In addition, end faces of the optical fibers and end faces to which a core of an optical waveguide is exposed are opposed and almost parallel to each other. Furthermore, the end face to which the core of the optical waveguide is exposed is provided so as to form an acute angle with a surface of the supporting substrate. Thus, tip ends of the optical fibers are not likely to be shifted from the core in a thickness direction of an optical waveguide device.