To provide a magnetic rotation sensor capable of improving the detection sensitivity with a simple structure using a magnetic sensing element by devising the arrangement of the magnetic sensing element and bias magnet and judging the dent and projection of a gear being a body to be detected.

This sensor has a Hall IC 2, containing a magnetic-sensing element 3 and bias magnet 1 supplying the magnet-sensing element with magnetic flux. The magnetic field measurement direction of the magnetic sensing element 3 and the magnetic flux generating surface of the bias magnet 1 are arranged to have a specific inclination angle which is not rectangular, for example 30 degrees to 60 degrees and is not parallel to a diameter direction P of the soft magnetic gear 4 to be a body to be detected in the constitution.