An image display system includes a display circuit which displays an image composed of a plurality of sub-images, an input circuit which inputs a certain image signal including at least one sub-image embedded in the certain image signal which is provided by at least one of fields and frames, a designating circuit which designates timings of composition positions of the sub-image on scan lines of the certain image, and one control circuit which controls at least one of an amplitude level and a DC level of image signals corresponding to an area of the sub-image detected by the timing designated by the designating circuit.