Data Communication System and Data Communication Method

An IP terminal 1 at a transmitting end has a copying unit 111 for copying packet data to be transmitted; an address setting unit 112 for adding unique address information to the respective copied packet data having the same contents; and a transmitting unit 113 for outputting, based on the address information, the copied packet data to different paths 1, 2 on an IP network 3. An IP terminal 5 has a selecting unit 523 for selecting and acquiring the first arriving packet data of the copied packet data having the same contents. In this way, for a data communication in a communication network such as Internet, a plurality of communication paths are used in a packet network, thereby reducing packet jitter and loss at the receiving end and providing a real time service having substantially the same quality as in a line exchanging network.