After a delivery tree is reorganized by a local processing, all terminal devices can recognize, in a short time, a delivery route as changed. In a local one of the terminal devices, if the local terminal device is a source node and further if the load of the CPU in any one of nodes exceeds a threshold value or the available band of the circuit line between nodes exceeds a threshold value, then a delivery tree organizing unit (462) determines nodes that receive a packet via such nodes and reselects a delivery route of the determined nodes. A packet structure modifying unit (464), if the local terminal device is the source node, modifies the header of a packet in accordance with delivery route information stored in a delivery route database (412). The packet structure modifying unit (464) then instructs, in accordance with the description of the header, a packet replicating unit (426) on a number of packet replicas and on the transmission destination of the packets.