Abstract: An indexing device wherein a rotary member which is supported by a support member such that the rotary member is rotatable about its axis and axially movable between a first position thereof and a second position thereof is rotated by a rotational drive mechanism having a one-way clutch, in increments of a predetermined angle, and wherein the rotary member is prevented by a stopper mechanism from being rotated past the predetermined angle due to inertia while being placed in the first position, and is precisely positioned by a positioning mechanism while being placed in the second position.