When a pixel and a signal line driver circuit are made up of semi-amorphous TFTs, an amplitude for driving the pixel has to be made larger, and a high power supply voltage is needed. The high power supply voltage increases power consumption in the case of partial drive. According to the invention, in order to reduce power consumption, a gate signal line driver circuit stores data of whether each gate signal line is used for displaying an image or not, thereby stopping driving of a gate signal line which is not required to be driven.