A dimming structure for an image display device further includes a contrast panel for altering contrast differences in a portion around an outputted image to achieve dimming effects on an image smaller than a light emitting lamp. In the dimming structure, a backlight unit has a plurality of light sources disposed therein. A display panel displays an image while the backlight unit is disposed to light the display panel. A contrast panel is disposed between the backlight unit and the display panel. The contrast panel has a light emitting window formed in a portion thereof corresponding to the image of the display panel to transmit light emitted from the backlight unit therethrough. The dimming structure assures uniform dimming effects on the portion around the image despite use of a light source bigger than the image to be outputted.