The display device has at least two set of maximum luminances including an image maximum luminance for displaying an image and an ordinary maximum luminance for displaying non-image information, the ordinary maximum luminance being lower than the image maximum luminance. The display device is capable of display at the appropriate brightness depending on the graphics to be displayed (whether it is an image or non-image information such as characters and menus) or in accordance with the operation done by the viewer (or operator) and which, when used as a monitor for medical diagnostic apparatus, allows for correct diagnosis by bright enough diagnostic images with good operability but without imposing any undue stress on the viewer's eyes.