An input/output apparatus is provided which is capable of preventing electric shock without reinforcing the insulation of a power-supply unit and capable of connecting to a USB, a LAN, or the like. An input/output apparatus includes a power-supply circuit that uses electric power as the power supply of the present apparatus, which is generated in a resonance circuit by an induction of an AC magnetic field from the resonance circuit on the apparatus main body side, and a communication circuit that transmits and receives a signal between a resonance circuit of the present apparatus and a resonance circuit on the apparatus main body side, and capable of being insulated from the power supply of the apparatus main body by receiving electric power from the apparatus main body in a non-contact state and by communicating with the apparatus main body in a non-contact state, thereby.