Abstract: Each of right- and left-deflection holograms is provided for a picture element in a vertical scanning line on the screen of a display unit. For example, the right- and left-deflection hologram are alternately arranged in a single vertical scanning line. A normal image is displayed through the picture elements corresponding to the right-deflection holograms while an inverted image is obtained by rotating the normal image by 180 degrees and is displayed through the picture elements corresponding to the left-deflection holograms. Thus, the two users sitting face to face with the screen of the display device between them can see the image displayed on the screen as a normal image. In addition to the images, a pair of markers are displayed on the screen. These markers are operated by a marker operating unit which moves one marker. The other marker is moved correspondingly by the same amount of movement in the 180-degree opposite direction.