Provided is a three-dimensional (3D) display system. The 3D display system synthesizes a 3D image and position information data of an observer obtained through a camera with an optimal viewing area image with respect to horizontal and vertical directions of a display panel in a 3D space, and displays the synthesized image on the display panel such that the observer can visually know an optimal viewing area. Accordingly, the 3D display system enables the observer to visually check the optimal viewing area with ease and induces the observer to move to a position in the optimal viewing area.