To reduce an input operation and improve a device operation rate by providing a means for setting a desired amount of money, a means for increasing/decreasing the displayed amount of money and a means for generating information showing the displayed amount of money.

A customer operation mechanism 1 is provided with a display part 1a consisting of CRT and the like, and an operation part 1b consisting of a transparent touch sensor panel provided on the display screen of the display part 1a. Transaction which can be executed is displayed on the screen waiting for a customer for permitting a user to select various transactions. The user selects the desired transaction from the screen. When the touches the display part, information is transmitted to a main controller part 2. The main controller part 2 starts a processing for the selected transaction. In such a case, an increasing key and a decreasing key are displayed on a sum input screen, and the sum can be set and changed without using a ten key by using the keys.