PURPOSE: To facilitate discrimination after cutting and quicken a classificating work, by a method wherein a marking device to sheet metal is provided in the vicinity of a shearing machine for marking.

CONSTITUTION: A marking device 8 is provided on a shearing machine 2. Sheet metal W is cut off by the shearing machine 2 in a predetermined shape programed in an NC device 7 beforehand. A side wall of a frame of a shearing machine 2 is provided with a labelling device 8 and a label 9 whose identification number and a mark on it are made to differ variously is stuck on a predetermined position of the surface of the sheet metal M prior to cutting of the sheet metal W. As the sheet metals cut by the shearing machine are provided with identifiable marks, classification of the product is made easy.