The magnetic sensor and optical sensor can be easily positioned so that their respective design positions are correct for the
magnet and
optical disc, respectively. [Solution] The rotation detection device 1 comprises a substrate 2 having an
insertion hole 10 for a rotating shaft 100, a
magnetic field forming member 3 that rotates with the rotating shaft 100, a plurality of magnetic sensors 20 arranged around the
magnetic field forming member 3, a casing 22 provided on the substrate 2 that houses the plurality of magnetic sensors 20, an optical sensor 6 provided on the substrate 2 on the opposite side from the plurality of magnetic sensors 20, and an optical disk 5 positioned opposite the substrate 2 with the optical sensor 6 in between, which rotates with the rotating shaft 100. The device has an adjustment mechanism that allows the position of the plurality of magnetic sensors 20 relative to the
magnetic field forming member 3 to be adjusted by adjusting the position of the casing 22 relative to the substrate 2 while the substrate 2 is positioned by adjusting the position of the optical sensor 6 relative to the optical disk 5.