PURPOSE: To improve the transmission efficiency of the whole network by providing an address control table where the addresses of terminal devices included in its LAN are registered and sending received packets only to a LAN which includes the destination terminal devices of the received packets.

CONSTITUTION: When the node device 500 receives a packet from a LAN 10, the transmission destination address SA of the received packet is registered newly unless the SA is registered in the address control table 802a, but when it is registered, it is found by retrieval whether the destination address DA1 of the received packet is registered in an AMT 802a or not; when not, the received packet is broadcast (together with an added broadcasting address DA2) to other all node devices 501∼503 in a repeating LAD 60 and when not, the received packet is discarded. When the node devices 501∼503 receive the packet from the repeating LAN 50 according to the broadcasting address DA2, the received packet is sent to its LAN on condition that the DA1 is registered in the AMT 802a, but if it is not registered, the received packet is discarded.