An input/output device includes a first sensor electrode and a second sensor electrode. In addition, the input/output device includes a first electrode and a second electrode which are electrodes for a display element, and a substrate sandwiched between the first sensor electrode and the second sensor electrode. The second sensor electrode is formed concurrently with the first electrode using the same material. The input/output device sensors a change in capacitance of a capacitor formed between the first sensor electrode and the second sensor electrode. Furthermore, a third sensor electrode to which a floating potential is applied may be provided to overlap with the first electrode. In the input/output device, either a liquid crystal element or a light-emitting element may be used, or both the liquid crystal element and the light-emitting element may be used.
