A rotary electrostatic encoder comprising a disk-shaped fixed plate having a first transmission electrode, a second transmission electrode, and four reception electrodes; a disk-shaped rotating plate having a first induction electrode superposed on and facing the first transmission electrode, and a second induction electrode positioned on the inside of the first induction electrode and superposed on and facing the second transmission electrode, a portion of the second induction electrode being a protruding eccentric circular part; transmission means for applying a transmission signal between the first transmission electrode and the second transmission electrode; and signal processing means for generating an output signal relating to the absolute rotational displacement of the rotating plate on the basis of two signal components generated from the four reception electrodes.