To provide a password code input method that makes it difficult to easily understand the contents of input operation, even if peek at the input operation is sneaked, when an operator inputs a password code for authenticating the operator as a regular operator to a device, such as a terminal machine of an ATM installed in a bank etc., which needs to authenticate an operator individual.

A password code input device is equipped with a means of realizing digit-by-digit input of a password code by single or multiple key input, and adding values of pressed keys to determine the digit-by-digit password code based on the sum. Since multi-key operation is carried out to determine to one number of the password code, even if sneak peek at the input operation is carried out, it becomes considerably difficult to understand its content, so that high effects on preventing peek sneaking can be obtained.