If both of LUN security information on storage apparatuses and configuration information on an iSNS server are acquirable, a management server makes reference to configuration situation of the LUN security acquired from a monitoring-target storage apparatus, thereby acquiring iSCSI initiator names which are permitted to access the storage apparatus. Moreover, the management server acquires, from the iSNS server, IP address of an iSCSI initiator name which does not exist on a monitoring-target host out of the iSCSI initiator names, then adding the IP address into monitoring-target nodes. Meanwhile, when an access from the management server to a monitoring-target node becomes impossible for a certain constant time-period due to a reason such that the monitoring-target node has been excluded from the network, the management server is capable of excluding the monitoring-target node from the monitoring targets on a GUI.