To provide a method and a device for straightening the warp at front and rear end width of a metal plate preferred to the metal plate in which high residual stresses easily remain inside such as a thick steel plate (in particular, a high-strength thick steel plate), and the front and rear ends (warp of the front and rear end width) are hardly straightened during the straightening by a roller leveler.

When any width warp is remained in front and rear ends in the longitudinal direction of a workpiece 1 to be straightened, the width warp in the front and rear ends is straightened by applying the repeated bending (bend-straightening) in the width direction to the front and rear ends by a straightening roll group 3.