A rotary encoder includes a control part having a storage section storing a plurality of parameters regarding error signal components at a reference rotation speed, the error signal components respectively being superposed on an “A”-phase signal and a “B”-phase signal in proportion to a rotation speed of a rotor body, and a rotation speed calculation section structured to measure a reception interval of a requirement signal and calculate a current rotation speed of the rotor body. The control part is structured to convert a parameter stored in the storage section to a value at the current rotation speed based on a ratio between the reference rotation speed and the current rotation speed, correction processing correcting the “A”-phase signal and the “B”-phase signal is executed based on the value converted, and the rotation position of the rotor body is calculated by using a corrected “A”-phase signal and a corrected “B”-phase signal.