The physiological change of eyes while viewing 3D TV was investigated. The change of pupil size was used as the measure of evaluation. The results are as follows : (1) The pupil size decreases after viewing 2D and 3D image and the the tendency is more critical with 3D images. (2) The indoor illumination has a significant effect on the pupil size in both 2D and 3D cases. (3) Less chage of pupil size were observed under the indoor illumination. Thus, if we only focus on the visual load on the eye, for viewing 3D image, it will be better to use indoor illumination.