An illumination apparatus comprises a control unit, an image capturing unit, a processor unit, a comparison unit, an adjustment unit and an illumination unit. The control unit generates a start signal in a predetermined time. The image capturing unit captures a plurality of images of ambient road condition according to the start signal. The processor unit extracts the edges of the vehicle from the captured images to obtain a current traffic. The adjustment unit generates different pulse voltages according to the different volume of traffic. The illumination unit emits light according to the different pulse voltages.