When a network composed of usual switches on a communication route exists, in the network, a QoS control cannot be carried out to a user. Specifically, the switch receives a packet and issues a notice to an external controller and a user authenticating section of the controller determines a QoS policy of a flow. When a plurality of networks exists on the route, a route calculating section selects a route based on the QoS policy and topology data so as to pass through an appropriate network. A flow table generating section generates a flow table which carries out queuing based on the QoS policy and a marking of a DSCP value to a DS field of a header when transmitting a packet to the selected network, and registers the flow table for the round-trip on the switch.