Disclosed herein are an apparatus, a method for measuring 3 dimensional positions of a viewer and a display device having the apparatus. The apparatus for measuring the 3 dimensional positions includes an image capturing module that photographs images included in objects; a detecting module that detects the objects from images photographed by the image capturing module and calculates sizes and coordinates of the images on the objects; and a position calculation module that calculates the 3-dimensional positions of the objects in the space in which the objects are positioned by using the information on the calculated sizes and coordinates of the image of the objects.