PURPOSE: To easily manufacture the bar structure with uniform mechanical strength, by bending the straight material like as pipe, rod or strip into the bar structure, in manufacturing the bar structure like as the door of gate., etc.

CONSTITUTION: A long pipe, rod, etc., is 180 degrees bent by the benders 2, 2', to form a lattice portion 3 with height l1. When the length l2 of the lattice portion 3 becomes the aim length, the position 5, a little longer than the length l2, is 90 degrees bent by the benders 2', 2', so as to form the laterally framing member 6. And then, the vertically framing member 7 is formed into almost same size as the height l1 of the lattice portion; next, the portion 11, through which the lattice portion 3 and the framing portion 10 are continued, is 90 degrees bent; hereby, the lattice member 3 and the framing portion 10 are formed into a bar structure. Finally, the discontinuous end portions 12, 13, of the member and the contact point 14 between the lattice portion 3 and the frame portion 10, are welded or calked, etc,; hereby, the bar structure is manufactured.