Abstract: A speed reducer employing rolling means comprises a casing, a high speed shaft connecting to an eccentric rod which has a variety of hollow pinion rollers disposed thereon. A plurality of slow speed shaft pins revolvably disposed in the pinion rollers respectively have one end opposite from the high speed shaft to connect to a slow speed shaft. A gear roller keeping ring is mounted on the pinion rollers for confining the pinion rollers thereto. A plurality of ring gear pins respectively enveloped with a ring gear roller for being rotatably engaged with the hollow pinion rollers, have their both ends connecting to the internal surface of the casing. Rotation of the eccentric rod drives revolution of the pinion rollers about the ring gear pins to actuate the slow speed shaft pins to revolve in the pinion rollers to achieve the speed reduction.