To improve the accuracy of workpiece positioning for machining via rotational displacement of stop members and gauge bodies.

This workpiece positioning device in shearing machines has a gauge body 9 partly integral with a stop member 5, on which a workpiece is pressed, and rotatable via a worm 45 and a worm wheel 43. The backlash in the worm gear is eliminated by the press the worm 45 gives to the worm wheel 43.