An operation mode acquiring unit compares before-expansion connection device information and after-expansion connection device information that are acquired by a device information acquiring unit, recognizes expanded device information on an external storage device that is expanded in a storage system, and acquires an operation mode that is applied to the storage system after the external storage device is expanded from a correspondence storage unit by using the recognized expanded device information. A setting executing unit executes the setting for the storage system accompanied with the expansion of the external storage device on the basis of the after-expansion connection device information acquired by the device information acquiring unit and the operation mode acquired by the operation mode acquiring unit.