1. A stereoscopic image display apparatus comprising: an image display panel; and a parallax barrier arranged apart from the image display panel by a predetermined distance, wherein the image display panel has a pixel pattern in which left-eye sub pixels and right-eye sub pixels are alternately arranged in horizontal and vertical directions, and wherein the parallax barrier comprises a plurality of parallax barrier pieces arranged in sizes and patterns that correspond to the sub pixels such that light is intercepted or transmitted so as to allow a left eye and a right eye to separately recognize a left-eye image and a right-eye image formed by the left-eye sub pixels and the right-eye sub pixels, respectively.