The punch nipper for section bars comprises a supporting arm (1), an operating arm (2) and a lever arm (3); the supporting arm (1) is a rectilinear element; on the distal end of the supporting arm (1) there is a support (4) which partially embraces the section bar; the operating arm (2) is a rectilinear element on the distal end of which there is an orthogonal element, onto which a point (2.1) directed at the support (4) is secured; the lever arm (3) is a rectilinear element to the distal end of which a cam-shaped body (3.1) is fixed; two pairs of brackets (6, 7) are fixed onto the supporting arm (1); the operating arm (2) is pivoted to the supporting arm (1) by means of a bolt (8) inserted into the first pair of brackets (6); the lever arm (3) is pivoted to the supporting arm (1) by means of a bolt (9) inserted into the second pair of brackets (7) and into the body (3.1).