Provided is a device for controlling luminance of a display, having a simplified ACL circuit compared to the prior art. The device for controlling luminance of a display calculates the average luminance (Y_avg) when video data is input, and determines the luminance variation (ΔY) according to the average luminance. The device for controlling luminance of a display may adjust the luminance of a display by controlling a current (driving current) that is used to drive a light-emitting diode included in a pixel, instead of modifying video data for the adjustment of luminance. That is, unlike the prior art, the device for controlling luminance of a display does not modify video data, for the control of luminance.