Provided is a light emitting device. Particularly, the light emitting device comprises a threshold voltage compensator. The threshold voltage compensator is connected between a gate and a drain of the driving TFT and has a gate connected to a second scan line to temporarily store at the storage capacitor a gate voltage reflecting a threshold voltage of the driving TFT in response to a second scan signal supplied by a second scan line and to transmit the data signal regardless of variations in the threshold voltage of the driving TFT when the output current is supplied to the light emitting diode.