An electro-optical device with a pixel portion of enhanced definition is provided, which uses pixels having a novel structure so that the number of stages of a source signal line side driver circuit is reduced to half the number of pixels in the horizontal direction, thereby making a space for placing the driver circuit and increasing the aperture ratio. One horizontal period is divided into the former half and the latter half. Signals for two adjacent pixels are successively inputted to one source signal line. A pixel selecting portion is provided between the two adjacent pixels. The signal selecting portion selects one of the pixels in the former half of one horizontal period so that a signal is written in the pixel whereas it selects the other pixel during the latter half of the horizontal period so that a signal is written in the pixel. Since one source signal line is shared between two adjacent pixels, the invention is advantageous also in terms of aperture ratio.