A multicore ultrafine coaxial wire is formed by consolidating a plurality of ultrafine coaxial wires in a flat array. Each of the ultrafine coaxial wires has a center conductor, whose tip portion is exposed, an insulating layer, an outer conductor, and a covering. The harness has a grounding member that connects in common the outer conductors of the multicore ultrafine coaxial wire and an insulator frame that fixes the center conductors. End portions of an underside film and end portions of a topside film both of the insulator frame are provided with an alignment hole to align the center conductors with circuits on a substrate.