A cold forged pulsar ring (1) which comprises a ring body (1a) having inner and outer peripheral surfaces. A plurality of circumferentially spaced gear teeth (2) are integrally formed by the use of a cold forging process with one of the inner and outer peripheral surfaces of the ring body (1a) so as to protrude radially of the ring body (1a). Each of the gear teeth (2) is so profiled as to have a substantially trapezoidal shape having a tooth angle (.theta.) not smaller than 5.degree., but not greater than 15.degree.. With this design, not only can a cold forging process be employed to manufacture the pulsar ring (1), but also a required output voltage can be secured from a sensor of the rotation detecting device in which the pulsar ring (1) is operatively employed.