A connector includes a housing and a plurality of contact module assemblies in the housing, wherein each contact module assembly includes a first signal contact module where a first signal contact body is inserted in a first resin molded part, a second signal contact module where a second signal contact body is inserted in a second resin molded part, and a ground plate, wherein the ground plate is sandwiched between the first signal contact module and the second signal contact module, so that a microstrip line structure is formed, and wherein, in the microstrip line structure, the first signal contact body and the second signal contact body form a stripline conductor, the first resin molded part and the second resin molded part form a dielectric board, and the ground plate forms a common ground conductor.