To provide an input device capable of certainly detecting a position of an input member.

A rotary input device 30 comprises: an electrostatic encoder 38 for outputting an output alternating current signal B shifted by a predetermined phase from a reference alternating current signal A in accordance with a position of a rotary member 31, on the basis of the reference alternating current signal A; and a control unit 42 for performing a timer interruption process on the reference alternating current signal A oscillated by an oscillator 45 at time intervals (at 1/10 second intervals) longer than one cycle (1/20 seconds) of the reference alternating current signal A. The control unit 42 detects a rising edge B1 of a waveform of the output alternating current signal B in a period t2 which is after the timer interruption process and before start of a next timer interruption process, obtains a phase difference between the reference alternating current signal A and the output alternating current signal B on the basis of a detection result of the rising edge B1, and obtains a position of an input member on the basis of the obtained phase difference.