PURPOSE: To enable the automatic checking of the correct position of the work and to improve productivity by letting the pawl of a pawl metal which is provided to a jig for checking position and is so formed as to project outward in the recessed position unexposed on the top surface of the work.

CONSTITUTION: The pawl metal 23 of a jig 21 for checking the position of the work W is mounted in the bottom end part of a jig body 21a and the metal 23 is turned according to the upward and downward movement of the jig 21. The pawl 23a is so constituted as to go into and from the jig body 21a according to the turning of the metal 23. In the evet of abnormality, the front bottom end of the pawl 23a is held in contact with the bed B but is projected by a size (m) from the bottom surface of the body 21a, by which the overall length of the jig 21 is increased. Provision is made to detect the increase thereof so that whether the work W unexposed with the key groove W'1 used as a reference for positioning on the top surface or penetrated with said groove from the top to the bottom surface is in the correct position or not is automatically detected.