PURPOSE: To provide an automatic deposite transaction system which can decide the use of a forged CD card as an illegal transaction and refusing this transaction even if the coincidence is secured with a password number.

CONSTITUTION: An automatic cash input/output machine 1 contains a CD card magnetic reading/rewriting device 7 which is connected to a center computer 2 via the communication circuits 3 and 4 and reads and rewrites a magnetic stripe 6 of a CD card 5. The computer 2 is provided with an authorized user deciding module 10 which retrieves a customer file 9 based on the customer information received from the machine 1 to decide whether a user is authorized or not, a latest using date check module 11 which collates the received data on the latest using date with the record of the module 9, and a latest using date updating module 14 which contains a function to update the storage area of the file 9 for the latest using date by the latest data when a transaction is complete and a function to send the data on the latest using date to the machine 1.