Disclosed herein is a 3-D image display unit that can be controlled flexibly to protect the user from eyestrain and operated easily. The 3-D image display unit includes measuring means for measuring a display time of a 3-D image, parallax adjusting means for instructing 3-D image forming means to adjust the parallax of the 3-D image. In the case where the 3-D image display time measured by the measuring means exceeds a predetermined time, the parallax adjusting means instructs the 3-D image forming means to reduce the parallax of the 3-D image to be formed, thereby the display means comes to display a 3-D image having a small parallax. The user can thus be protected from eyestrain.