A medical image display device is provided to effectively synthesize a plurality of three-dimensional images to reduce operators labor and to enable time necessary for an image diagnosis by means of the synthesized image to shorten. Objects or synthesized images are displayed at two or more display regions. The medical image display device selects one object displayed at each display region by a pointing device and moves the selected object to other display regions. The moved object is synthesized with an object displayed at the other region and the synthesized object is displayed at its corresponding region. Additionally, in the case where a plurality of objects are displayed at one display region, a plurality of objects are synthesized and the synthesized objects are displayed at the display region.
