An image display apparatus includes: a lighting unit which includes a lamp unit, and illuminates light onto a display screen; a power supply unit which supplies electric power to drive the lamp unit in the lighting unit; a main circuit unit which outputs a brightness control signal to control brightness of the lighting unit, and controls the power supply unit; and a constant voltage generator which is provided between the main circuit unit and the power supply unit, and controls magnitude of the brightness control signal which is output from the main circuit unit, to generate a constant voltage, wherein, by detecting over-current flowing in the lamp unit, the main circuit unit outputs the brightness control signal to apply a corresponding voltage to the lamp unit according to a form of the over-current, or activates the constant voltage generator so that the brightness control signal can be controlled by the constant voltage generator.