A simple means is used to realize a virtual network communication via an home network and Internet. A relay device 4 comprises bridge module 12 provided between a network protocol stack 13 and each of network devices 10, 11 for bridging for packets which are not addressed to the relay device or VLAN, or not broadcast request packets; a server address storage section 17 for storing the global address of a server; a tunneling session establishing section 20 for establishing a tunneling connection with the server based on the global address; a capsulating processing section 21 for capsulating a originating address and sending it to the server via the tunneling connection; and a virtual IP address/private IP address conversion section 22 for decapsulating a packet addressed to the relay device, converting a destination virtual network address included in this packet to a private IP address on the LAN of a client apparatus, and sending it onto the LAN via the bridge module.