To provide an interior illuminator for an automobile that prevents light leakage to the driver's seat and light reflection in a window glass, can illuminate a backseat more evenly with an adequate quantity of light, consumes less electric power, generates less heat, has a small size and can be produced at a reduced cost.An interior illuminator has: cold cathode tubes 5, 6; a cold cathode tube driving circuit for driving the cold cathode tubes 5, 6; manipulation switches 12, 13, 14 and 15 for turning on and off the cold cathode tubes; and a housing 2 that houses the cold cathode tube driving circuit and holds the cold cathode tubes and the manipulation switches. The housing 2 is attached in a position on a longitudinal center line of the automobile and behind the driver's seat, and the cold cathode tubes 5, 6 each have an illumination range set to be lower than the lower edge of a window glass behind the driver's seat.