To prevent signal jamming by exchanging information between a transmitting unit and a receiving unit with the surface of a human body as a medium.

When a part of a human body 12 comes in contact with a door handle 20 of an automobile, a transmit request signal S1 is transmitted from a receiving unit 14 to the transmitting unit 13 side through the human body 12 in contact. A command signal S2 responding to the transmit request signal S1 is then returned to the receiving unit 14 from the transmitting unit 13 through the surface of the human body 12 in contact, and a driving motor 27 for locking/unlocking a door is driven on the basis of the command signal S2.