PURPOSE: To provide the small sized sound input output device with small power consumption.

CONSTITUTION: A thin film 12 able to be vibrated is provided to a silicon semiconductor substrate 11, an electrode 17 is arranged to the outside of the thin film 12 and an opposite substrate 13 is arranged to the silicon semiconductor substrate 11 via a support 15 and an electrode 14 is formed to an inner surface of the opposite substrate 13. Then the vibration of the thin film 12 by an incident sound wave is detected as a capacitance change between a couple of the electrodes 14, 17 and the thin film 12 is vibrated by an electrostatic force through the application of a voltage to a couple of the electrodes 14, 17 to input/output sound.