A disclosed balanced transmission cable connector includes a relay board having a wiring pattern extending from the upper face to the lower face through a via hole. Wire connection pads to output signals are disposed on the upper face of the relay board, and wire connection pads to input signals are disposed on the lower face of the relay board. Two wires of a pair wire are soldered to the wire connection pads disposed on the same face of the relay board. A ground layer inside the relay board shields between the soldered parts of the pair wire to transmit output signals and the soldered parts of the pair wire to transmit input signals.