The image display apparatus includes a flat-shaped transmission display device for displaying an image, a backlight corresponding to the display device and a control unit for controlling the backlight in such a way that a part of the backlight corresponding to a non-image area is turned off based on information concerning the image to be displayed. The apparatus is capable of cutting unnecessary light so as to be suitably used to the image diagnosis in a medical field and improving the visibility of the displayed image in the region of interest.