To prevent illegal copy without damaging the convenience of a legal user.

At the time of using digital information, a registration number corresponding to the digital information to be used is transmitted from a terminal equipment 2 to an information management center 1. The information management center 1 confirms the use condition of the digital information pertinent to the received registration number, transmits data indicating the permission of use to the terminal equipment 2 when it is a legally available state, and transmits data indicating the inhibition of use to the terminal equipment 2 when it is a legally unavailable state. The terminal equipment 2 allows the digital information to be used only at the time of receiving the data indicating the permission of use. Thus, it is difficult for a user to illegally change the use condition, and the number of times of use or available period of the digital information can be exactly managed.