Each of illumination portions 30a includes a bulb terminal VT electrically connected to a first electrical contact 31a of a bulb 31 and a battery wire B, a courtesy terminal CT which is electrically connected to a third electrical contact 32d of a switch 32 and a bypass wire P, and can be electrically connected to a second electrical contact 31b of the bulb 31 when an electrical contact member 32f of the switch 32 is brought into a position of FIG. 5, and a switch terminal ST electrically connected to a first electrical contact 32b of the switch 32 and a grounding wire G. The courtesy wire C and the bypass wire P can be electrically connected together by a mode-changing switch 33.