A capacitance detecting apparatus includes: a first on/off switch; a first reference capacitor; a second on/off switch; a third on/off switch; a first sensor electrode; a fourth on/off switch; a second reference capacitance; a fifth on/off switch; a sixth on/off switch; a second sensor electrode; a comparator; switch controlling means for alternately repeating a second switch operation and a third switch operation following a first switch operation; counting means for counting a number of times for repeating the second switch operation; and judging means for judging changes in capacitances related to the first and second sensor electrodes, based upon the number of times for repeating the second switch operation counted by the counting means before a level of voltage at the first input terminal and a level of voltage at the second input terminal are reversed.