A three-dimensional display system, comprising: a glassesless-type 3D image display in which a parallax barier including apertures is disposed in front of a display panel; a camera configured to obtain background image coordinate information on an actual observing area including an observer present in front of the 3D image display; a 3D image obtainer configured to receive the obtained background image coordinate information from the camera and obtain a 3D image and position information data of the observer using stereo matching; and a controller configured to calculate an extended intensity distribution of light, which is based on an intensity distribution in an observing area, wherein the observing area is part of a plane parallel to a display panel plane, emitted from light sources of the glassesless-type 3D image display and reaching respective views in an observing area extended in an x direction of a horizontal axis, parallel to the display panel plane, and in a z direction of a vertical axis with respect to an observing plane, obtain intensity distribution data in horizontal and vertical observing ranges from the observing plane, also obtain an optimal viewing area image having quantities of light at respective views in horizontal and vertical directions of the display panel using the intensity distribution data, synthesize the 3D image and position information data of the observer, which serves to determine a position of an observer present in front of the 3D image display, obtained from the 3D image obtainer with the optimal viewing area image wherein, when the 3D position information data of the observer obtained from the 3D image obtainer does not correspond to the optimal viewing area, the controller controls the display panel to display optimal view position guide information such that the observer moves to a position in the optimal viewing area characterized in that, the optimal view position guide information comprise a display of the synthesized image on the display panel comprising the observer as obtained by the camera and a plurality of areas (A, B, C, D), one of the areas indicating an optimal viewing area an the remaining areas indicating that the 3D image is gradually shown worse in the respective areas, such that the observer visually detects an optimal viewing area. the a glassesless-type 3D image display in which a parallax barier including apertures is disposed in front of a display panel; a camera configured to obtain background image coordinate information on an actual observing area including an observer present in front of the 3D image display; a 3D image obtainer configured to receive the obtained background image coordinate information from the camera and obtain a 3D image and position information data of the observer using stereo matching; and a controller configured to calculate an extended intensity distribution of light, which is based on an intensity distribution in an observing area, wherein the observing area is part of a plane parallel to a display panel plane, emitted from light sources of the glassesless-type 3D image display and reaching respective views in an observing area extended in an x direction of a horizontal axis, parallel to the display panel plane, and in a z direction of a vertical axis with respect to an observing plane, obtain intensity distribution data in horizontal and vertical observing ranges from the observing plane, also obtain an optimal viewing area image having quantities of light at respective views in horizontal and vertical directions of the display panel using the intensity distribution data, synthesize the 3D image and position information data of the observer, which serves to determine a position of an observer present in front of the 3D image display, obtained from the 3D image obtainer with the optimal viewing area image wherein, when the 3D position information data of the observer obtained from the 3D image obtainer does not correspond to the optimal viewing area, the controller controls the display panel to display optimal view position guide information such that the observer moves to a position in the optimal viewing area