PURPOSE: To provide a device and method for straightening bends of metallic materials with a high precision by having a structure in which a measured bend quantity and an actual bend quantity correspond easily to each other.

CONSTITUTION: In a forming line where a straightening device 3, 4 and a travelling cutter 5 are successively provided along the moving direction of a metallic material 1, an optical measuring device 8, by which the position of the tip end part of the metallic material is measured in both horizontal and vertical directions with the material cantilevered by plural pinch rolls 6, 7, is provided behind the travelling cutter. A measuring distance L from the center of the last pinch roll to the measuring coordinate of the measuring device is set for 150 to 450mm; after proofreading the measuring coordinate, the measured position of the tip end part of the metallic material is converted to a bend quantity in a longitudinal direction; and the straightening quantity of the straightening device is controlled by the converted bend quantity.