An opening area between twisted portions of a pair of twisted wires is arranged to be opposite to an opening area of an aperture antenna of each of communication apparatuses. Thus, the use of the pair of twisted wires permits division of electric power among the communication apparatuses and also communication of signals. In particular, among the opening areas between the twisted portions of the pair of twisted wires, only an opening area, which is in between the twisted portion and the twisted portion and is opposite to the aperture antenna, is formed to be larger than a different opening area. This provides a vehicular power line communication system and a transmitter in the system; the system strengthens electromagnetic induction connection between the transmitter and the receiver to permit power line communication.