A storage system 1 including: a plurality of data storage systems 3000 each including a storage apparatus 5000 providing a data storage area to an external apparatus 1000, and an information processor 4000 controlling data input and output between the external apparatus and the storage apparatus, the storage system comprising; a data attribute information retention part 4420 holding data delete allow/disallow information 4423 and data attribute information 4421 and 4424; a management information retention part 2420 that is a list holding at least one of data attribute information 2421, and data storage location information 2422 of each piece of data; and a data delete control part 4440 receiving a data delete command and controlling a process of deleting the data stored in the storage apparatus based on the command. Upon receipt of the data delete command, the data delete control part sets to the file determined to be identical from being deleted when determining that the file identical to the delete target exists in the storage system.