The vertical/horizontal amplitude control device for controlling a vertical amplitude and a horizontal amplitude of an image display device for displaying a video signal includes a brightness level detector for detecting a brightness level of the video signal, a vertical amplitude controller for controlling the vertical amplitude based on the brightness level, and a horizontal amplitude controller for controlling the horizontal amplitude based on the brightness level. The device controls the vertical and horizontal amplitudes into constant without a delay from a change of a video signal even when the brightness level of the video signal abruptly changes.