A light, compact angle-of-rotation sensor is comprised of a magnetic ring within which resin is used to fix the ring to the periphery of a shaft. Formed on the magnetic ring are insets into which the resin enters, providing a strong bond between the resin and the magnetic ring. In addition, a key inset into the shaft provides a strong bond between the resin and the shaft. Magnetized zones are formed on the outer surface of the magnetic ring, and magneto electric transducer means are arranged in the proximity of these zones to face said zones, and the angle of rotation is detected from the changes in magnetism that accompany the rotation.