To easily and clearly discriminate a stain on a display screen by displaying a dark-color image on the display screen when a cleaning mode for cleaning the surface of a touch panel input means is specified.

When the cleaning mode is specified by inserting a key that a service engineer or cleaning person carries into a reset key cylinder 8 for maintenance and rotating it after various transactions regarding cash are carried out according to input information from the touch panel input device, the dark- color image is displayed on the entire display screen of a color liquid crystal display 10 of the touch panel input device. Thus, a stain sticking on the touch panel of the display screen of the color liquid crystal display 10 are clearly seen, so the cleaning person can easily and clearly discriminate between the stained part and unstained part of the touch panel, so that the stain can securely be wiped away without being left.