A detection unit has a detection element for detecting a change of magnetic field according to a rotation of a magnet, and an angle calculator for calculating an angle signal according to a detected physical quantity detected by the detection element. Further, a storage stores a plurality of correction values for correcting detection error of the angle signal, and another storage stores a plurality of correction values for correcting detection error of the angle signal. An abnormality determiner determines abnormality of the correction values, an another abnormality determiner determines abnormality of the correction values. A control calculator performs a control calculation by using the angle signals corrected by using the correction value having been determined as normal.