A light emitting display device comprising: a display region including a pixel adapted to emit light in response to a data signal, a scan signal, and an emission control signal; a controller for controlling brightness of the display region; a scan driver for supplying the scan signal and for controlling a signal width of the emission control signal in accordance with a signal output from the controller; a data driver for supplying the data signal corresponding to video data, and a power source supply unit for supplying power to the display region, wherein the controller is adapted to control an amount of current supplied to the display region in accordance with a sum of the video data in one frame; CHARACTERISED IN THAT: the data driver is arranged to correct the data signal using a gamma correcting signal output from the controller; and in that the controller is further adapted to output the gamma correcting signal corresponding to ambient light; wherein the controller comprises: a brightness controller for selecting a gamma correcting value in accordance with brightness of the ambient light to control the data signal using the gamma correcting signal corresponding to the gamma correcting value; and an emission controller for controlling the amount of current supplied to the display region in accordance with the sum of the video data; wherein the brightness controller comprises: an optical sensor for outputting an analog sense signal corresponding to the brightness of the ambient light; an A/D converter for converting the analog sense signal to a digital sense signal; a counter for counting a predetermined number in one frame to generate a counting signal corresponding to the counted number; a conversion processor for outputting a control signal; a register generator for storing a plurality of register set values; a first selector for selecting one register set value among the plurality of register set values stored in the register generator in response to the control signal set by the conversion processor to output the one register set value; and a gamma correcting circuit for generating the gamma correcting signal in accordance with the control signal of the conversion processor. a display region including a pixel adapted to emit light in response to a data signal, a scan signal, and an emission control signal; a controller for controlling brightness of the display region; a scan driver for supplying the scan signal and for controlling a signal width of the emission control signal in accordance with a signal output from the controller; a data driver for supplying the data signal corresponding to video data, and a power source supply unit for supplying power to the display region, wherein the controller is adapted to control an amount of current supplied to the display region in accordance with a sum of the video data in one frame; the data driver is arranged to correct the data signal using a gamma correcting signal output from the controller; and in that the controller is further adapted to output the gamma correcting signal corresponding to ambient light; wherein the controller comprises: a brightness controller for selecting a gamma correcting value in accordance with brightness of the ambient light to control the data signal using the gamma correcting signal corresponding to the gamma correcting value; and an emission controller for controlling the amount of current supplied to the display region in accordance with the sum of the video data; a brightness controller for selecting a gamma correcting value in accordance with brightness of the ambient light to control the data signal using the gamma correcting signal corresponding to the gamma correcting value; and an emission controller for controlling the amount of current supplied to the display region in accordance with the sum of the video data; wherein the brightness controller comprises: an optical sensor for outputting an analog sense signal corresponding to the brightness of the ambient light; an A/D converter for converting the analog sense signal to a digital sense signal; a counter for counting a predetermined number in one frame to generate a counting signal corresponding to the counted number; a conversion processor for outputting a control signal; a register generator for storing a plurality of register set values; a first selector for selecting one register set value among the plurality of register set values stored in the register generator in response to the control signal set by the conversion processor to output the one register set value; and a gamma correcting circuit for generating the gamma correcting signal in accordance with the control signal of the conversion processor. an optical sensor for outputting an analog sense signal corresponding to the brightness of the ambient light; an A/D converter for converting the analog sense signal to a digital sense signal; a counter for counting a predetermined number in one frame to generate a counting signal corresponding to the counted number; a conversion processor for outputting a control signal; a register generator for storing a plurality of register set values; a first selector for selecting one register set value among the plurality of register set values stored in the register generator in response to the control signal set by the conversion processor to output the one register set value; and a gamma correcting circuit for generating the gamma correcting signal in accordance with the control signal of the conversion processor.