In one embodiment of the present invention, a display module includes a display screen divided in a vertical direction into screen regions in each of which an image can be independently displayed. A control device for controlling an image display operation of the display module includes: upper- and lower-screen data selectors for each dividing an input image signal in accordance with a corresponding one of the screen regions; and upper- and lower-screen time-division gradation conversion blocks for each generating a display signal for each of a plurality of sub-frames from an image signal, corresponding to a corresponding one of the screen regions, which is outputted from a corresponding one of the data selectors. This makes it possible to provide an image display device in which, even when a sub-frame display is carried out, the voltage of an image signal can be applied to a pixel for a longer time so as to be sufficiently applied to the pixel.