The purpose of the present invention is to improve a worker's technique for tightening nuts and bolts. Provided are a plurality of bolts (4-1, 4-2,..., 4-N) set up so as to be tightenable, axial force sensors (sensors 10-1, 10-2,..., 10-N, and load cells 24) for detecting the axial force (F) applied to each bolt, and a comparison means (information processing device 12 and PC 28) for associating identification information (76) for each bolt and the detected axial force, and comparing the detected axial forces between the bolts. Thus, the tightening of nuts and bolts with an appropriate fastening force can be performed, and the safety of components to be tightened can be increased.
