PURPOSE: To improve the quantity of communication understanding between private networks by simplifying the setting processing of a communication line for a connection device whose address to a destination communication network is not clear and dispersing the quantity of communication of a multiple address communication line to an individual communication line as communication is much activated.

CONSTITUTION: A connector at a sender side implements multiple address transfer (103) of a communication packet with an address of a communication network of a sender, an equipment address of the sender and an equipment address of a destination added thereto by using a multiple address communication line when an address of a destination communication network is not clear, and a connector at a receiver side writes a sender communication network address and an equipment address of the information received through the multiple address communication to a destination address management table, and the operation is repeated, then each connector generates a cross reference between an address of the destination communication network and the equipment address into an address management table, and the address of the communication network stored in the table is used at a next and succeeding connection request to set an individual communication line and to transfer information.