PURPOSE: To produce bar-shaped steel materials having a desired form efficiently in a plant consecutively, by providing rotary bending devices freely movably in left and right sides on a line including a bending point of a press bending device and bending the bar-syaped steel material successively from the outside end part.

CONSTITUTION: A bending core Ga of a rotary bending device GA placed in the outmost side rises by an oil cylinder and is stopped, and a required number of bar-shaped steel materials (a) is supplied from a rack for supplying of materials to required work positions of a press bending device F and rotary bending devices GA and GB. Next, a bending force applying rod material Gb of the device GA is driven to bend both end parts of the steel material (a). After that, the rod material Gb and the core Ga are returned to original positions. After the steel material (a) is bent similarly by the device GB, a bending force applying member Fb of the device F is driven, and the steel material (a) is pressed to the side of a receiving member Fa to bend the center of the steel material (a). In this case, the steel material placed in the right of a press point Fp is bent while passing on an inclined plate to form a hoop.star lapped steel bar for construction.