To provide a small dome light apparatus which uses a flexible flat cable for attaching it on the ceiling of a car or the like.

By providing an A contact part, which connects one lead wire of a dome lamp to a 1st electricity feeding conductor of a 3 core electricity- feeding-conductor flat cable, by providing a C contact part in a 2nd electricity feeding conductor, by providing a B contact part, which connects to the other side lead wire of the lamp, in a 3rd electricity feeding conductor and an E contact part insulated from the B contact part, by connecting a common terminal P to the above the B contact part. By connecting an R middle terminal to the common terminal P and the above E contact part, and a Q middle terminal to the above C contact part, the room lamp instrument for cars is characterized by constituting so that it may electrically conduct or cut between above common terminal P and the above Q middle terminal, or an R middle terminal by the s movable terminal.