To substantially simplify the control of carrying members, hoisting heavy members and execution of construction by miniaturizing the members to be carried in a work site, substantially simplify the quality control in production by reducing welding quantity in member production and disassemble and reassemble freely at needs after assembling members into a steel frame.

A collar-like lower joint metal fixture 8 as a lower locking material is provided around a small diameter steel pipe 6, and a large diameter steel pipe 7 is fitted around the small diameter steel pipe 6, and a collar-like upper joint metal fixture 11 as an upper locking member is fitted to the protrusion of the small diameter steel pipe 6 protruding upward from the large diameter steel pipe 7 and is lowered to the upper end position of the steel pipe 7 and is jointed to the end of a beam steel skeleton 4 such that the beam steel skeleton 4 is held by the lower joint metal fixture 8 and the upper joint metal fixture 11, and the large diameter steel pipe 7 as a column body pipe 10 is fitted to the end of the small diameter steel pipe 6.