1. An image processing device comprising: detecting means for detecting a luminance of an input video signal representing a target image, and comparing the detected luminance with a predetermined threshold so as to extract an over-luminance video signal representing an over-luminance area; filtering means for applying an operation to the over-luminance video signal so as to remove a hole or a chunk existing in a detected area; zebra pattern generating means for generating a zebra pattern video signal and overlapping the zebra pattern video signal with the processed over-luminance video signal so as to generate and output a first mixing signal formed by mixing the zebra pattern video signal and the over-luminance video signal; signal mixing means for mixing the first mixing signal and the video signal representing the target image to generate and output a second mixing signal; and a display for displaying the image having the zebra pattern overlapped on the detected over-luminance area, based on the second mixing signal.