A display device includes a display panel which includes pixels arranged in a matrix form and a controller which receives a first image signal corresponding to a first active period of a first frame, outputs a first final output signal corresponding to a first conversion active period of the first frame, and drives the display panel based on the first final image signal. The controller includes a timing changing unit which receives the first image signal and changes a first image signal pixel size corresponding to the first image signal to a panel pixel size corresponding to the display panel to generate the first output signal, and a frequency changing unit which receives the first output signal from the timing changing unit and reduces a frame frequency of the first output signal based on the first image signal to output the first final output signal.