To uniformly roll down each flange of a shape steel by arranging a straightening roll of cantilever structure to be abutted on an inner surface of a flange of the shape steel parallel to the flange of the shape steel.

A shape straightening apparatus 21 is provided with a first straightening roll 22 to be rotated while abutted on an outer surface of a flange of a wide flange beam 20, a second straightening roll 23 to be rotated while abutted on an inner surface of the flange, and a second straightening roll support frame 24 which movably support one neck part of the second straightening roll 23 in the direction parallel to the thickness direction of the flange, and is tiltably arranged relative to the plane of the flange. In addition, a tiltation regulating mechanism 25 to tilt the second straightening roll support frame 24 in the direction opposite to the tilting direction by abutting the support frame on an inner surface of the flange.