According to the present invention, it is possible to enhance a performance in accessing a storage system, without performing data migration process between the storages constituting the storage system. A virtualization controller 2 connecting a host computer 1 and a storage 3 constituting the storage system controls a plurality of access paths (path such as port 6-backplane 9-port 6, port 6-backplane 9-storage controller 7-port 6) provided within the virtualization controller. It further performs a control so that an optimum access path is selected for switching, out of the plurality of access paths, based on setting information from a management server 4 by a system administrator and various monitoring results detected by the virtualization controller itself.