A storage apparatus, which controls the input and output of data to and from a computer, includes a logical volume for storing data from the computer, a common resource for storing data pre-stored in the logical volume as update data in order to store subsequent data from the computer in the logical volume, an encryption/decryption unit for encrypting or decrypting data stored in the logical volume or update data stored in the common resource, and a key change unit for changing a key for encrypting or decrypting data stored in the logical volume. The storage apparatus changes the key for encrypting or decrypting update data stored in the common resource based on information of the key used for data stored in the logical volume.