The present disclosure relates to an electrical connector and an assembling method thereof. The electrical connector includes a first insulating housing, a step-shaped second insulating housing, a plurality of first contacts, a plurality of second contacts, and a plurality of third contacts. The first and third contacts are exposed over the second insulating housing and face the same direction. The second contacts are exposed over the second insulating housing and face an opposite direction. The exposed first, second, and third contacts are capable of being soldered to a transmission cable.