To eliminate the extra care of inputting identification numbers at each transaction while accomplishing accurate checking to see if card users are right persons and minimize the possibility of letting other persons know the identification numbers in the inputting thereof.

At transactions requiring checking to see if users of cards are right persons made through transaction terminals, the identification numbers are inputted once, the transactions are conducted and then, the cards are withdrawn. Thereafter, further transactions are permitted without requiring the inputting of the same identification numbers within a specified exemption period. This is not confined to the same transaction terminals and permits transactions at other transaction terminals without requiring the inputting of the same identification numbers. Thus, when the identification numbers are inputted once into any of a plurality of terminals and transactions are conducted, further transactions can be done within the specified exemption period thereafter.