In order to prevent a rapid decrease in luminance of a screen as an average picture level (APL) increases, a display device for controlling luminance of an image through a peak luminance control (PLC) curve may comprise a display unit and a controller configured to obtain a first average picture level (APL) of a first image, to determine whether a second APL of a second image is increased compared to the first APL as the first image is switched to the second image, and to control image quality of the second image to reduce an output level of the second image when the second APL is increased compared to the first APL.