A storage system for controlling attributes for data stored in virtual storage areas includes a logical storage area management unit 1140 that manages the linking of virtual storage areas and attributes such as encryption attributes to logical storage area groups. When receiving a command to change an attribute of a virtual storage area or virtual volume, the logical storage area management unit determines the presence or absence of a unit logical storage area in a logical storage area group or pool linked to a different attribute and that is not yet allocated to a virtual storage area. The logical storage area management unit links a unit logical storage area determined to be present to a virtual storage area, reads data stored in the unit logical storage area linked to a virtual storage area subjected to an attribute change, and stores the read data in accordance with the different attribute.