To provide a highly browsable data processing device, provide a highly portable data processing device, provide a data processing device which consumes low power, or provide a data processing device having high display quality, the data processing device includes a display portion having flexibility, a plurality of driver circuit portions arranged in the periphery of the display portion, a sensor portion discerning an external state of the display portion, an arithmetic portion supplying image data to the driver circuit portions, and a memory portion storing a program executed by the arithmetic portion. A first mode in which the display portion is unfolded or a second mode in which the display portion is folded is sensed by the sensor. Luminance adjustment processing is carried out by the program in accordance with the first mode or the second mode.