To improve the productivity of metal cutting by synchronizing such metal cutting and the machining precision detection thereof.

The metal cutting attachment comprises a worktable 1 to which a work 2 is secured, a tool magazine 15 that stores a plurality of cutting tools 16, an automatic tool changer for changing a cutting tool 11 set on a main spindle 10 for another on the tool magazine 15, a device main body attached to the main spindle 10 to rotate the tool 11 and move it three-dimensionally in relation to the work 2 so that the work 2 is cut accordingly, and a wear detecting means 20 for optically detecting the outer shape of the cutting tool 11 set on the main spindle 10 to measure the abrasion loss of the cutting tool 11. The outer shape of the cutting tool 11 set on the main spindle 10 is thus measured before and after cutting so that the cutting precision is tested on the basis of the abrasion loss by cutting of the cutting tool 11.