The overall processing function of a storage apparatus is improved by suitably migrating ownership.The storage apparatus comprises a plurality of microprocessors; a plurality of storage areas formed in a drive group configured from a plurality of physical drives; and a management unit which manages, as the microprocessors which possess ownership to the storage areas, the microprocessors which handle data I/Os to/from one or more storage areas among the plurality of storage areas, wherein the management unit detects variations in the processing loads of the plurality of microprocessors, selects a migration-source microprocessor which migrates the ownership and a migration-destination microprocessor which is the ownership migration destination on the basis of variations in the processing load, and determines whether to migrate the ownership on the basis of information on a usage status of resources of each of the storage areas to which the migration-source microprocessor possesses ownership.