An organic light emitting display device includes a display area including a plurality of pixels connected to scan lines, light emission control lines and data lines; a scan driver electrically connected to the display area through the scan lines and light emission control lines; a data driver electrically connected to the display area through the data lines; an optical sensor for generating an optical sensor signal corresponding to the brightness of the ambient light; a first luminance control unit for providing a first luminance control signal for controlling a gamma-corrected gray level voltage of a data signal in accordance with the optical sensor signal; and a second luminance control unit for providing a second luminance control signal for controlling a pulse width of the light emission control signal in accordance with the optical sensor signal and the data of one frame.