A file management method, whereby inconsistencies can be prevented between a file recorded in a memory card and the file management information that a terminal apparatus manages, without leaking the information of a file made and stored in an in-card processing system. According to this method, a flash memory accessible from two processing systems 100 and 300 is provided. First processing system 100 requests a reservation of an use area of flash memory 200a to second processing system 300, which, upon receiving the request, implements a reservation processing for an area of the memory section and reflects the information of the reserve area upon file management section 230. First processing system 100 performs the processing of writing data into the area reserved by second processing system 300. Inconsistencies between the file management information that a terminal manages and a file actually recorded into the memory section of a secure card can be prevented. Furthermore, exclusive control can be implemented, whereby there will be no direct access from a terminal to the area used for a card-dedicated file recorded therein by means of processing that takes place inside the card.