PURPOSE: To easily remove a danger that a password is known by others by inputting a new password to be changed directly by a customer himself through a 2nd input means and changing a file in a center through a line.

CONSTITUTION: When a customer proposes the change of his password to a bank clerk through a written application (no password is written) in case of requiring the change of the password, the bank clerk selects password changing processing by a 1st input means 7. Receiving the selection, a 1st display means 6 displays a password changing picture to the bank clerk and a 2nd display means 3 displays a guidance instructing the input of the ordinary password to the customer. The customer inserts a card or a bankbook into a window transaction device and inputs the ordinary password through a 2nd means 4. A comparing means accesses the center based on the ordinary passwords and the data read out through the card or the bankbook, compares the input data with the password obtained by said accessing, and when the coincidence of both words is confirmed, the customer inputs a new password through the 2nd input means 4 in accordance with a guidance displayed on the 2nd display means 3.