The storage apparatus includes 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 microprocessors which handle data I/Os to/from one or more storage areas among the plurality of storage areas. The management unit detects variations in the processing loads of the plurality of microprocessors, generates load balancing target information which includes information on the storage areas to which the ownership is migrated, information on the migration-source microprocessor serving as the migration source of the ownership, and information on the migration-destination microprocessor serving as the migration destination of the ownership, and migrates the ownership to the storage areas with timing such that there is no drop in the processing load of the migration-destination microprocessor contained in the load balancing target information.