Disclosed herein is a display device for preventing a luminance floatation phenomenon in a low grayscale region. The display device includes a display panel, an external input interface configured to receive an image signal from an external device, and a controller configured to adjust a gamma value when an input frequency of the image signal is less than an output frequency of the display panel and a variable refresh rate (VRR) function for changing the output frequency according to the input frequency is activated and to output the image signal to the display panel based on the adjusted gamma value.