A display device capable of reducing power consumption and preventing luminance changes, and a driving method thereof are provided. The display device includes: a display panel displaying a still image and a motion picture; a signal controller controlling signals for driving the display panel; a graphic processing unit transmitting input image data to the signal controller; a light source unit irradiating the display panel with light; and a light source driver controlling signals for driving the light source unit, in which the signal controller includes a frame memory storing the input image data and controls the display panel so as to be driven at a first frequency or a second frequency, and the light source driver drives the light source unit at a first ratio when the display panel is driven at the first frequency and at a second ratio when the display panel is driven at the second frequency.