PURPOSE: To make it possible to reciprocate a follower which is coaxially arranged with a prime mover in association with the rotation of the primary mover, with a simple construction, both follower and prime mover being formed each in a shape of an obliquely cut cylinder, by mating the oblique surfaces of the follower and the prime mover with each other.

CONSTITUTION: A prime mover A fitted on a rotary shaft 1 and a follower B which is inserted in a stationary plate 3 and in which a slide key 2 is embedded are formed of cylinders having diameters and wall thickness which are equal to each other, respectively, and further, they are arranged coaxially with each other, being mated together with their similar oblique surfaces. The follower B is pressed against the prime mover A by means of a coil spring 4. Even if the prime mover A is rotated, the cam follower B is reciprocated along the same axis while the slide key 2 preventing the cam follower from being led into rotation. Accordingly, it is possible to reciprocate the follower on the same axis with a simple construction.