An RFID notification unit enables an RFID reader to regularly read the RFID code of an RFID tag attached to the relevant terminal itself, its user and its current location and transmits the RFID code to a server. Upon receipt of this code, the using qualification determination unit of the server determines the current using qualification of the terminal referring to a using condition storage unit. When a user attempts to open an important information file, a file using control unit issues a request to the server. A permit determination unit determines whether to permit the opening of the relevant file, based on the using qualification and the storage contents of a file/level storage unit. When the opening is permitted, the important information file is downloaded onto the terminal or its decoding key is returned.