To identify a logical topology of each virtual network among logical topologies of a plurality of virtual networks configured in physical devices.A management server includes a controller for managing logical topology information of all virtual networks each of which includes a plurality of virtual resources configured in a plurality of physical devices coupled to a network; wherein the controller: searches the logical topology of all the virtual networks from the entire virtual network based on the information of branch point resource which is a kind of virtual resource for mutually coupling the plurality of virtual networks and constitutes a branch point for each virtual network; extracts a series of virtual resources that terminates at the branch point resource; and identifies the series of extracted virtual resources as a partial topology, which eventually represents the topology of a virtual network inside the entire virtual network.