A parallax barrier 3D display utilizes adjustable at least one parallax barrier for having an observer always retrieve stereo vision no matter whether horizontal or vertical movements towards the parallax barrier 3D display are made. The parallax barrier is adjustable in its width and a distance from the parallax barrier 3D display, or a parallax barrier having an appropriate width or distance may be chosen from each parallax barrier set. Therefore, the observer does not have to search for sweet spots nor keep on staying at the sweet spots for retrieving stereo vision.