Abstract: The invention relates to a device (1) for the continuous lengthening of a metal strip (2) by traction, said device comprising, in the strip transporting direction (R), at least three S-roll units (3, 4, 5, 6, 7) each provided with at least two rolls (8, 9 10, 11, 12, 13, 14, 15, 16, 17). According to the invention, the rolls (8, 9, 10, 11, 12, 13, 14, 15, 16, 17) are positioned in such a way that the metal strip (2) is wound round them at a roll periphery angle (a) of more than 180°, and at least the second S-roll unit (4) in the strip transporting direction (R) comprises two rolls (10, 11) with different-sized diameters (D10, D11).