A pair of cylindrical magnets with cut away portions has been arranged on both sides of a magnetic sensing element in symmetry of rotation, and a yoke surrounds the magnetic sensing element in contact with outer peripheral surfaces of the pair of the cylindrical magnets with cut away portions. The pair of the cylindrical magnets with cut away portions rotates around an axial center with a concurrent axial displacement along with a rotation of a rotating body. The pair of the cylindrical magnets with cut away portions is arranged in inclined manner against an axis-of-rotation of the magnet. Thereby, the rotation and the displacement in the direction of the axis against the magnetic sensing element of the pair of the cylindrical magnets with cut away portions, and the number of times of rotation can be detected by detecting the size of the magnetic flux density by the magnetic sensing element. The pair of the cylindrical magnets with cut away portions improves the size and linearity of the magnetic field on the axial center.