A 3D image display device includes a display unit including a display panel and an optical panel located at a front side of the display panel and changing a path of light. A controller is configured to generate a signal for controlling the display unit. The controller includes an image signal processor which generates an input image signal based on image information containing 2D image information and depth information. The image signal processor generates a 3D image signal based on the 2D image information and the depth information. The image signal processor extracts a low-depth area having a small depth and generates a 2D image signal corresponding to the low-depth area. The display unit displays the low-depth area by a 2D image.