An input device contains a resistance-element series formed by series-connected resistance elements, low resistors opposing the resistance elements, an operating object which brings one of the low resistors into contact with one of the resistance elements and changes the contact area therebetween, an output point at the midpoint between resistance elements, and a controller. When the resistance element and low resistor are not in contact, the input device enters a sleep mode in which the resistance-element series or low resistors have a high potential and the other a low potential. In the sleep mode, determination that the operating object has been operated occurs when a change in voltage or current on the low potential side is detected. A voltage is applied across ends of the resistance-element series, and the device enters a detection mode in which the output is based on the contact area change.