A position detection error correcting method that corrects position detection errors using a limited storage capacity, by calculating position detection error correction values by four simple arithmetic operations at startup to reduce a startup time delay and consumption of a storage capacity even when a portion containing steep error variations exists. Detection error correction values of a position detector are expressed by a correction function using a periodic function, and correction parameters of the correction values are stored in advance in a non-volatile memory. At startup, these correction parameters are read out, and a position detection error correction value corresponding to each detected position is calculated and stored in a random access memory. The output position detection error correction value detector corresponding to each detected position is read out from the random access memory and a corrected detected position value corrected for the detected position value error is calculated.