An optical sheet for three-dimensional images and a three-dimensional image display device using the same, are discussed. According to an embodiment, the three-dimensional image display device includes a display unit to display two-dimensional images using unit pixels each including at least three colors of sub-pixels, and an optical sheet to convert the two-dimensional images into a plurality of different three-dimensional images, and the neighboring three-dimensional images are overlapped with each other by a predetermined range. With the above described configuration, the curved lenses are tilted to provide neighboring viewers with three-dimensional images overlapped with each other by 15% to 60%. As a result, a ratio of the horizontal and vertical display resolutions of the three-dimensional images can be equal to a ratio of the horizontal and vertical display resolutions of the two-dimensional images, and the quality of three-dimensional images can be improved.