Accuracy of photodetection is improved. A method for driving an input-output device which includes a light unit, a display circuit, and Y (Y is a natural number of 2 or more) photodetectors is provided. The same photodetection control signal is input to the Y photodetectors. The light unit is lit while the Z light-emitting diodes are sequentially switched and emit light in a frame period set by the display selection signal. In a cycle that is longer than a cycle of switching the lighting states of the light unit, Y pieces of data based on the illuminance of light incident on the Y photodetectors are generated in a period during which the light unit is lit.