The present invention provides a liquid crystal display device used in miniaturized portable equipment which exhibits favorable display quality while decreasing a load applied to a driver circuit which supplies a video signal line to pixel electrodes. In a liquid crystal display device which includes liquid crystal display elements and a liquid crystal driving circuit, a boosting circuit is provided to a pixel portion. The boosting circuit, after writing a video signal in a pixel electrode and one electrode of a boosting capacitance, brings the pixel electrode into a floating state. Then, by applying the video signal to another electrode of the boosting capacitance, a voltage of the pixel electrode is boosted or dropped.