A data transfer device 210 is equipped with a plurality of communication ports 211a and 211b, a communication establishment processor 212, and a communication maintenance processor 213. The communication establishment processor 212 transmits and receives communication establishing information for establishing communication with an external device connected via the communication port to and from the external device. The communication maintenance processor 213 is configured to operate independently of the communication establishment processor 212 and, every time a predetermined transmission period elapses, transmits communication maintaining information for maintaining the establishment of communication with the external device, to the external device. In a state that communication with a plurality of external devices via the plurality of communication ports is established, the data transfer device 210 transmits data received from one of the plurality of external devices to the other one of the plurality of external devices.