An object is to provide a driving method of a liquid crystal display device with a low power consumption and a high image quality. A pixel includes a liquid crystal element and a transistor which controls supply of an image signal to the liquid crystal element. The transistor includes, in a channel formation region, a semiconductor which has a wider band gap than a silicon semiconductor and has a lower intrinsic carrier density than silicon, and has an extremely low off-state current. In inversion driving of pixels, image signals having opposite polarities are input to a pair of signal lines between which a pixel electrode is disposed. By employing such a structure, the quality of the displayed image can be increased even in the absence of a capacitor in the pixel.