An LED substrate comprises holes having an elliptical shape through which fixing screws are inserted. The fixing screw has a head portion, an unthreaded neck portion whose diameter smaller than that of the head portion, and a threaded shaft portion whose diameter smaller than that of the neck portion. A major axis of the hole is larger than the diameter of the head portion, and a minor axis thereof is smaller than the diameter of the head portion and larger than the diameter of the neck portion. The LED substrate further comprises counterbored recesses to which anchoring claws provided in a cabinet are fitted. A width of the counterbored recess in a direction of the major axis of the hole is larger than that of the anchoring claw. The counterbored recesses are formed on both of two sides of the LED substrate facing each other in a first direction.