ROTARY ENCODER

A rotary type encoder is provided with a signal generating portion 2 for generating a sine wave signal of N periods for each revolution in accordance with the rotation of the shaft 4 of a motor; a calculation means for obtaining the rotation angle of the shaft 4 based on the sine wave signal; an EEPROM 37 being arranged in a manner that the error value of the rotation angle for one revolution of the shaft 4 thus measured is divided in relation with the N periods to set a plurality of first angle regions i, the angle region almost at the center of the angle region i is divided into plural regions to set second angle regions j, and an error value corresponding to the angle at almost the center of each of the angle regions j is stored therein in correspondence with the rotation angle; and a correction means for reading the error value stored in the EEPROM 37 in correspondence with the rotation angle to correct the rotation angle.