To avoid or minimize formation of a swell due to a worn end grove by a comparatively inexpensive method by providing a means of moving the upper and the lower working rolls in the axial direction.

Roll chocks 7 are provided with a cylindrical surface 5 and suitable for rolling a long workpiece 10 made of a metal. A driving device 12 is provided for the purpose of moving rolls 1, 2 right or left in the axial direction. With the rolls 1, 2 shifted by a distance S in the axial direction and either left or right, they are displaced by forming an angle α1 or α2 to a line perpendicular to the passing line of the mill. This is because forces act on the rolls 1, 2 by the chocks 7 as the chocks slide along inclined contact plate surfaces 11 on the corresponding Mae West blocks 8, 9. Generally, the displacement S1 and S2 in the axial direction can be different from the crossing angle α1 and α2 of the top and bottom rolls.