An intra-vehicle LAN system combining electric power supply includes a main controller having control signal generation device for generating a control signal used to control each of on-vehicle electric equipments and outputting the control signal to an electric power supply line through which electric power is supplied to the electric equipments and an electric equipment control unit being provided between the electric power supply line and each of the electric equipments to detect the control signal transmitted through the electric power supply line and to control each of the electric equipments. In this system, the generated control signal contains an ID for specifying each of the electric equipments.