A display device compensates a threshold voltage Vth of a driving transistor according to a source follower internal compensation method. The threshold voltage Vth of the driving transistor is sampled in advance before one horizontal period H, so that a sufficient time for sampling the threshold voltage Vth of the driving transistor can be obtained even in a high-speed or high-resolution display device. Furthermore, the compensation rate of the internal compensation circuit is improved to reduce luminance deviation between the pixels.