An operating device includes a touch panel 21 having a display 22 on which a screen is displayed and an input element 23 having a plurality of electrodes and outputting a signal corresponding to capacitance generated between a ground potential and each of the electrodes, an input signal processor 14 receiving the signals output from the electrodes of the input element 23, recognizing a touched position touched by an operator, and generating an operation signal corresponding to the recognized touched position and transmitting the generated operation signal to a controller 3, and determiner 16 determining whether the input element 23 is electrically stable or not. When the input element 23 is determined to be electrically unstable, the determiner 16 displays a warning screen or warning window on the display 22.