A content using system is composed of a content importing apparatus and at least one content using apparatus. The content importing apparatus includes a content ID generating unit that generates a content ID, and a content key information encryption converting unit that converts the encryption of content key information by using an encryption key ("network key") that is shared in advance on the network. The content using apparatus includes a content key information decrypting unit that decrypts the content key information, whose encryption has been converted, by using the network key, a moved content list storing unit for storing a moved content list (MCL) in which the content IDs of contents that have been written onto a storage medium are written, and a moved content list managing unit that judges whether the writing of a content is permitted or prohibited based on the MCL.