A network system includes a storage unit that stores topology information in a graph database in chronological order, the topology information including end point information and connection information of logical resources of the virtual network, end point information and connection information of physical resources of the physical network, and correspondence information between the logical resources and the physical resources; a setting information acquirer that acquires setting information of the virtual network from the orchestrator using a change notification from the orchestrator as a trigger; and a topology information management unit that updates the topology information stored in the graph database of the storage unit on the basis of the acquired setting information.