A management computer comprises: a cascade configuration storage section which stores volume cascade configuration information which is information related to the configuration of the volume cascade; an expansion target volume determination section which determines any logical volume of the plurality of logical volumes as a target of expansion; a cascade configuration specifying section which specifies, from the volume cascade configuration information, other logical volume of the volume cascade to which the expansion target logical volume belongs; and a capacity expansion control section which transmits, to the storage system group, a capacity expansion instruction which designates two or more target volumes and the capacity obtained after expanding each of the two or more target volumes, the two or more target volumes constituting a target volume cascade comprising the expansion target logical volume and the specified other logical volume.