Rotation angle sensor and correction method for the same

A rotation angle sensor, comprising:

• a ring magnet that is provided around a rotating shaft subjected to rotation angle detection so as to be integrally rotated with the rotating shaft and is magnetized so as to have not less than one pair of magnetic poles with different polarities arranged in a circumferential direction;
• a magnetic field sensor that is provided so as to face the ring magnet in a radial direction of the rotating shaft and detects magnetic field strengths in radial and tangent directions of the rotating shaft;
• a rotation angle calculation section that calculates a rotation angle of the rotating shaft based on the magnetic field strengths detected by the magnetic field sensor;
• a correction value storage section that stores correction values preliminarily set for each magnetic pole, or each pair of magnetic poles, facing the magnetic field sensor;
• a facing magnetic pole detecting means that detects the magnetic pole or the pair of magnetic poles facing the magnetic field sensor;
• and
• a rotation angle correcting section that refers to the correction value storage section, extracts correction values corresponding to the magnetic pole or the pair of magnetic poles detected by the facing magnetic pole detecting means, and corrects a rotation angle calculated in the rotation angle calculation section by using the extracted correction values.