In a load control unit, three R, G, and B LED chips that constitute each light source (33a-33d) of reading lamps (25-31) and a connector (35) with a built-in controller are mounted on a circuit board (37) to thereby eliminate the connection of a controller (35b) built into the connector (35) with the built-in controller and the respective light sources (33a-33d) by signal lines. In addition, the controller (35b) and a lighting ECU (43) are connected by a multiplex communication line (39), and the multiplex communication line (39) is routed in pillars (15, 17) of a vehicle (1). Consequently, the number of wires can be reduced compared with when individual wires connected to the respective light sources (33a-33d) are passed through the pillars (15, 17), and thereby making it possible to effectively use limited spaces within the pillars (15, 17) through which many other wires are passed.