PURPOSE: To judge the clamp state of a work with certainty by making the clamp state of the work so as to be judged by a variation in the resistance value of a strain gauge installed in a clamper, in a unit which clamps the work by a laser beam machine or the like.

CONSTITUTION: In this work clamper unit 1, a strain gauge 25 is attached to a nearby spot of the work clamp part of a clamper 27 clamping a work W. In addition, a clamp judging means, which takes out a variation in the resistance value of this strain gauge 25 and thereby judges a clamp state of the work W, is connected to this strain gauge 25. Accordingly, when the work W is clamped by the clamper 17, a strain being given to the strain gauge 25 is detected by the clamp judging means as a variation in the resistance value, through which whether the work W is surely clamped or not, namely, the clamp state is surely judgeable by a degree of the variation.