An apparatus for adjusting the stroke of a light projector of a button setting machine includes a rod connected at its one end to the light projector, a holder holding the opposite end of the rod and pivotably connected to one end of a pivotable actuating lever pivotally movable in response to the reciprocating movement of an upper pusher, a leaf spring acting between the actuating lever and the rod to urge the latter upwardly, a spring urging the actuating lever to turn in a direction to retract the light projector from a path of movement of a punch, and an adjustable stopper engageable with the actuating lever to limit pivotal movement of the same against the force of the spring. With this construction, the light projector has a stroke considerably shorter than the stroke of the upper pusher and can be adjusted independently of the stroke of the upper pusher.