PURPOSE: To display a color picture without adding a display memory, a display control circuit, etc., by providing CRT monitors for black-and-white picture and those for color picture in a ratio of 3:1 and providing a switching circuit which inputs video signals to respective CRT monitors.

CONSTITUTION: Video signals for black-and-white picture or color picture which are outputted from display control circuits 2a to 2c are switched by a switching circuit 5. That is, they are inputted to CRT monitors 3a to 3c for black-and white picture respectively at the time of display of a black-and-white picture, and three video signals corresponding to CRT monitors 3a to 3c for black-and- white are inputted as signals of red R, green G, and blue B of a CRT monitor 4 for color picture at the time of display of a color picture. Thus, one CRT monitor 4 for color picture is only added to three CRT monitors 3a to 3c for black-and-white picture to display a color picture without especially adding a display memory, a display control circuit, etc., for color picture display.