An output signal V1=sin θ is output from a first magnetic sensor and an output signal V2=cos(θ+α) is output from a second magnetic sensor. An output signal correction unit in a rotation angle computing device corrects the output signal V2 from the second magnetic sensor to an output signal V2′ (=cos θ) so that a positional phase difference (90°+α) between the magnetic sensors and is made equal to a target phase difference of 90°. A rotation angle computing unit computes the rotation angle θ of a rotor based on the corrected signal V2′ (=cos θ) and the other output signal V1 (=sin θ).