Provided are a display device and a driving method thereof. The driving method of a display device including first pixels emitting lights or transmitting and reflecting an external light, and second pixels corresponding to the first pixels respectively, includes calculating light emission amounts necessary for the respective first pixels for realizing an image signal, receiving the light information on the amount of the external light incident to the first and second pixels, calculating a reflection light amount of a reflection device according to the external light amount, comparing the light emission amounts necessary for the respective first pixels with the reflection light amount, and adjusting light emission amounts of the respective first pixels according to a result of the comparing.