When both a key insertion detecting switch (a push switch in an intelligent key system vehicle) and a buckle switch are off, a room lamp is controlled so as to be extinguished. Even when the key insertion detecting switch is off and the buckle switch is on, the room lamp is controlled so as to be extinguished. When the key insertion detecting switch is off and the buckle switch changes from on to off, the room lamp is lit, and a timer incorporated within a CPU starts counting. When a predetermined time period has elapsed, the room lamp is automatically extinguished.