PURPOSE: To observe a natural stereoscopic image in a wide observation range while utilizing the parallax between both eyes by projecting an image for the left eye and that for the right eye alternately on one projection screen, and the observing the left and right images separately through spectacles which vary in light transmissivity on the left and right sides alternately synchronizing with said projection switching.

CONSTITUTION: While an image for the left eye is projected on a screen 7 by a projector 2, a switch 4 is placed on the left-eye side for closure and then the left-eye light shielding plate 61 of spectacles 6, e.g. a liquid-crystal plate increases in light transmissivity to observe the image with the left eye 81. During this period, the right-eye light shielding plate 62 has light transmissivity and the image is not seen with the right eye 82. When a film 1 is advanced by one frame and an image for the right eye is projected, the left and right are inverted. This operation is repeated ≥10 times per second to observe a stereoscopic image. Even when the projection screen is observed at a different position, the image is separated and seen, so that stereoscopic visible range is wide and a natural stereoscopic image is obtained only by being seen through the spectacles.