A display device includes a gray scale controller which adjusts the number of pieces of image data successively displayed at the same brightness level to a predefined value or less when a desired brightness level represented by input image data is equal to or less than a predetermined level. Alternatively the display device may include a gray scale controller which may make the frequencies of selection of an immediately lower display brightness level than a desired level and an immediately higher display brightness level closer to each other when the brightness level represented by the input image data is equal to or less than the predetermined level and other than a plurality of display brightness levels. This frequency control is done to prevent a selected display brightness level from continuing at the same level over a period greater than a predetermined cycle.