A coded card on which are written, by way of a card writing means, prescribed digits and characters, expressed in a box figure code having four segments. Information on the location of card matching data is written into a matching data position recording area in an initial code area. When read by of a card reader, if the matching data is present in the places indicated in the position information in the matching data position recording area, the card is judged to be genuine. However, if the matching data is not present in the places indicated in the position information, it is judged to be of a fake card made by recombining portions of a used card with a new low value cards.