There is a need to generate a virtual network across multiple physical networks without the need for users to understand information about the respective physical networks.A network system includes: multiple communication systems for communication with a user; multiple physical network management servers that manage multiple physical networks including multiple routers; and a virtual network management server that manages a virtual network connecting the communication systems with each other through the physical networks. The virtual network management server acquires physical network configuration information. The virtual network management server generates management information in order to manage the physical networks as one abstraction network. The virtual network management server configures the abstraction network by transmitting the generated management information to each of the physical network management servers and the routers.