An active matrix light emitting device which is capable of clear color display of multiple gray scales and a driving method hereof is provided. The light emitting device has a pixel portion, and the pixel portion has a plurality of pixels. Each of the plurality of pixels has an EL element, a first EL driver TFT, a second EL driver TFT, a switching TFT, and an erasure TFT. The first EL driver TFT and the second EL driver TFT are connected in parallel. The method of driving the device includes inputting a digital video signal outputted from a source signal line driver circuit, and forming n write-in periods and (m-1) erasure periods within one frame period, wherein m is an arbitrary number from 2 to n, wherein display and non-display periods are specifically defined, and wherein the plurality of EL elements are selected to emit light or not to emit light in the display periods in accordance with the digital video signal.