PURPOSE: To enhance work efficiency by rotating an insertion hole-bored pipe at a position opposed to both ends of a metal net and in the longitudinal direction of an outer peripheral surface equivalent to a lattice spacing of the metal net and inserting the both ends of the metal net into the insertion hole and welding and fixing the contact area.

CONSTITUTION: Horizontal bars and vertical bars are assembled in the shape of a lattice so that a metal net 3 may be laid out. An insertion holes are installed to a pipe 2 in the longitudinal direction of the outer peripheral surface at a position opposed to both ends of the metal net 3 and at a spacing equivalent to a lattice spacing of the metal net 3. Then, the pipe 2 is supplied one by one and rotated so that the insertion hole may be directed at the both ends. Then, either the pipe 2 and the metal net 3 or both the pipe 2 and the metal net 3 are moved so that both ends of the metal net 3 may be inserted into the insertion hole. Then, a contact area between the metal net 3 and the pipe 2 is welded and fixed.