Each of at least two terminal apparatuses uses content data in accordance with license information which is generated by a content distribution system to which it subscribes. A conversion apparatus includes a working area for storing license information which is compatible with one of the terminal apparatuses, and a central processing section for converting the license information stored in the working area into license information which is compatible with the other terminal apparatus. Thus, there is provided a conversion apparatus which can convert one's own license information so as to be passable to others.