PURPOSE: To simply observe a high definition picture on a CRT monitor with a few scanning lines by using two CRT monitors, displaying an entire image resulting from thinning some of display picture elements on one monitor and displaying a picture in the visual center corresponding to the picture element on the other monitor.

CONSTITUTION: A digital picture data sent to a picture processing unit 4 via a picture fetch device 2 and an A/D converter 3 whose picture elements are N×N (N is a prescribed number) or over is displayed on two CRT monitors 100, 101 whose picture elements are less than the number N. Then the entire image of the picture is displayed on the monitor 100 while the picture elements are properly thinned out and the central partial image of the picture is displayed on the other monitor 101 without thinning out. Thus, a high definition picture is simply observed by using the CRT monitors 100, 101 with a few scanning lines.