PURPOSE: To make uniform a thickness and a width of a metal band manufactured by rolling concurrently by adjusting the bending strength in the lateral direction of the metal band by giving a bending tension in the longitudinal direction and a bending in the lateral direction to the meal band concurrently and giving the metal band a plastic elongation by an elongation percentage obtained by a specific equation.

CONSTITUTION: When the metal band 2 having a larger thickness and a larger width than those target values is elongated by a tension leveler 1, the bending strength in the lateral direction is adjusted by giving a bending tension in the longitudinal direction and a bending in the lateral direction to the metal band 2 concurrently and the band 2 is given a plastic elongation by an elongation percentage of l obtained by the equation 1 to correct a thickness and a width of the band 2 to be the target values, respectively. Two types or more of crown rollers including flat rollers are installed as work rollers 11 of the tension leveler 1. A bending strength in the lateral direction throughout the total corrective process is adjusted by independently adjusted rolling drafts of every crown roller.