1. An image display device, comprising: a region of interest extraction unit that generates a depth image signal by depth image conversion employing a depth threshold, the depth image signal including information on a distance in a three-dimensional space between a viewpoint and each pixel of a two-dimensional image including a region of interest desired to be noted by an observer, the depth image conversion being such that a depth value indicating the distance between the viewpoint and each pixel of the two-dimensional image is converted to a depth value for 2D display when the depth value is equal to or larger than the depth threshold; a parallax image generation unit that generates a left-and right-eye parallax images each having a parallax in the region of interest and having no parallax in a region other than the region of interest, from said two-dimensional image and an image obtained by conversion of a region of interest image to be displayed in the region of interest at each of right and left viewpoints, based on said two-dimensional image and said depth image signal; and a 3D image display unit that displays the left-eye parallax image and the right-eye parallax image.