An input/output device includes a display circuit which changes its display state in accordance with a display data signal; a plurality of photodetector circuits which generate optical data in accordance with illuminance of light entering the photodetector circuits; wherein the photodetector circuits each include X (a natural number of 2 or more) photoelectric conversion elements; X charge accumulation control transistors in which one of a source and a drain is electrically connected to a second current terminal of one photoelectric conversion element of the X photoelectric conversion elements, and one charge accumulation control signal of X charge accumulation control signals from the photodetector circuit control section is input to the gate; and an amplifying transistor in which a gate is electrically connected to one of the source and the drain of each of the X charge accumulation control transistors.