A touch-panel cellular phone specifies an invalid area not accepting a user's input operation on a touch panel in advance. The cellular phone detects a user's touch area on the touch panel so as to execute a function pre-assigned to the touch area not encompassed by the invalid area. Additionally, it is possible to reduce and display menu icons in the display area precluding the invalid area on the touch panel. Thus, it is possible to prevent an error operation when a user holding a cellular phone inadvertently touches the touch panel.