It is made possible to correctly decrypt data in a storage area in a computer system (storage system) having various encryption execution sections (such as a storage device or encryption appliance having an encryption function). In the case where storage areas may be encrypted by the various encryption execution sections, there is a possibility that, when a storage area is copied or the configuration of the computer system is changed, the storage area cannot be correctly decrypted unless it is managed where the storage area has been encrypted or whether the storage area is not encrypted. To prevent this, a management computer manages the key and the encryption execution section for each storage area in the system. Furthermore, when copying a storage area or the like is performed, the management computer determines which storage area's state and key should be changed together with performing the copy operation is performed, and instructs the encryption execution section to change the state and key for the storage area if it is necessary to change it.