A plug connector coupled to a receptacle connector is presented, comprising: a conductor for signals; a ring-shaped conductor for ground, the conductor for ground surrounding the conductor for signals; a ring-shaped insulator surrounding the conductor for signals and being surrounded by the conductor for ground, and insulating between the conductor for signals and the conductor for ground; a lower body; and an upper body coupled onto the lower body. The conductor for signals includes a lower portion protruding below a first portion of the top of the insulator, a middle portion inserted into a hollow portion of the first portion, and an upper portion protruding above the first portion. The conductor for ground includes a lower portion protruding below the first portion and an upper portion surrounding the first portion. The lower body includes a lower housing, such that the upper portion is accommodated in the hollow portion.