A conductive contact holder includes a holder substrate that is made of a conductive material. The holder substrate has a first opening section for holding conductive signal contacts, and a holding member that is made of an insulating material and that is arranged into the first opening section for holding at least one of the conductive signal contacts. The largest outer diameter of a surface of the holding member parallel to a surface of the conductive contact holder is larger than the smallest interval between longitudinal axes of the conductive contacts held in the conductive contact holder.