A mobile information terminal has a front surface on which a display surface of a display device is arranged and a rear surface on which a plurality of operation keys are arranged. The mobile information terminal further has a half-depressing sensor for detecting that each of the operation keys is half-depressed and/or a touch sensor for detecting that each of the operation keys is touched. A control section executes a processing operation to cause the display device to display an image showing the arrangement of said operation keys and to change an icon which corresponds to a key of operation keys when a control section determines, according to an input signal from the half-depressing sensor or the touch sensor, that the finger of the operator is placed on this key of operation keys.