This device includes: an input unit for receiving a shape of an inspection target surface of a wedge exposed from a slot with no force applied to the wedge; a relation storage unit which acquires and stores, as a deformation reaction force relation, a relation between a reaction force of a spring at the inspection target surface of the wedge and deformation distribution from the shape of the inspection target surface of the wedge inputted to the input unit; a measurement unit for measuring measurement deformation distribution of the inspection target surface of the wedge; an estimation unit for estimating an estimation reaction force from the measurement deformation distribution and the deformation reaction force relation; and a judgement unit for judging proper/fault about looseness of the wedge from the estimation reaction force.