A three-dimensional display device including an image display unit having first pixels corresponding to left-eye images and second pixels corresponding to right-eye images. The first and second pixels define an image formation plane for substantially forming the images. A parallax barrier is placed in front of the image display unit, and has light interception portions and light transmission portions alternately and repeatedly arranged in a horizontal direction of the image display unit to separate left-eye image light beams from the first pixels and right-eye image light beams from the second pixels in directions of left and right eyes of a viewer. The light interception portions and the light transmission portions define an image separation plane for substantially separating the light beams.