A transmitter equipped with a plurality of transmission path ports and a relay section. The relay section has a routing table and a router. In the routing table, information about the relay of the received packet to one of the transmission path ports connected to a relay transmission path is stored, correlated with both a port identifier of each the transmission path port and the source address of the transmitter that transmitted the packet. The router extracts the port identifier of the transmission path port that received the packet and the source address contained in the received packet, and routes the received packet to the transmission path port connected to the relay transmission path by referring to the routing table for the extracted port identifier and the extracted source address.