A display device and data driver are provided. The display device includes a plurality of data drivers provided for a predetermined number of data lines in a plurality of data lines. The plurality of data drivers receive the serialized video data signal from the display controller, generate a modulated data timing signal whose period changes within the one frame period, and supply a gradation voltage signal to each of the predetermined number of data lines for each of data periods based on a data timing of the modulated data timing signal, each of data periods corresponding to the data timing of the modulated data timing signal.