An input detection system includes a detection device including a plurality of detection electrodes arrayed in a detection region, and an input support device including a first electrode, a second electrode provided so as to be movable on a concentric circle about a rotating axis overlapping with the first electrode, and a coupling portion that electrically couples the first electrode and the second electrode. A position of the rotating axis of the input support device is fixed to the detection region of the detection device, and a reference potential is supplied to the detection electrode corresponding to the first electrode and a drive signal is supplied to the detection electrode corresponding to the second electrode.