There are provided a device and method for supporting an external device I/O using a mobile communication terminal that the mobile communication terminal held by an individual may be used as an I/O unit of the external device, which is driven by the external device, for example, a kiosk and a digital signage, rather than driven by the mobile communication terminal. Further, a plurality of users may simultaneously perform I/O of the external device using each of the mobile communication terminals held by the plurality of users.