A content management method and content storage system are provided in which a content key encrypted with a first storage key and stored along with a content encrypted with the content key in a first content storing means is decrypted with the first storage key, the content key obtained by the above decryption is encrypted with a newly generated second storage key and stored along with the encrypted content in a second content storing means. Thus, the content management method enables to safely duplicate (back up) a content while preventing the content from being copied fraudulently.