When an end portion of a three-dimensional image appears to pop forward from a display surface, a predetermined end area is set at a periphery of images forming the three-dimensional image to modify at least one of the images to modify the stereoscopic effect so that at least a part of the end portion appears to be level with the display surface. A disparity between corresponding pixels in the end area of the images is modified so that the disparity is gradually decreased toward the end of the images, and image parts at left and right areas of the end area of a reference image among the images are deformed based on the disparity. At least one of the images is modified by modifying the image other than the reference image with the deformed image parts of the end area. Then, three-dimensional processing is applied to the modified images.