A storage apparatus includes a storage unit and a controller, wherein control of inputting/outputting data from/to a device provided in said storage unit is executed in accordance with a request received by said storage apparatus. An actual device of the storage apparatus corresponds to a virtual device which is external to said storage apparatus. The controller operates to perform a process for mapping an actual device address corresponding to a virtual device address, in accordance with a specification of the actual device to be mounted or unmounted to correspond to the virtual device, and storing and retaining mapping information obtained from the mapping in a first table. The controller also performs data input/output process for receiving, an access request for data input/output in which said virtual device address is specified, obtaining the actual device address mapped to said specified virtual device address in said first table, and accessing the actual device by said obtained actual device address.