PURPOSE: To perform crown straightening of a strip and to wind the straightened strip by using a roll capable of changing the roll profile by inserting ring pistons having tapered surface into annular space as a backup roll.

CONSTITUTION: By extracting proper ones of the ring pistons 14, 14', 15, 15' outside, the outer diameters of the backup rolls 4', 5' are reduced partially. On the contrary, by inserting the proper ones of the ring pistons 14, 14', 15, 15' inside, the outer diameters of the backup rolls 4', 5' are expanded partially to prevent the bending of the work roll and the crown straightening of the strip is performed as expected. The strip with the crown straightened excellently in such a way is wound in the down coiler finely.