PURPOSE: To improve execution accuracy by arranging a plurality of steel plates having connecting parts to a steelwork beam on both ends outside the pillar main reinforcement, and providing a fireproof formwork outside the steel plate.

CONSTITUTION: Steelwork beams 22 are connected with the right and left, the front and rear of a steelwork pillar 21, and reinforcing plates 3 are respectively fixedly secured between the flanges and the webs of the respective steelwork beams 22. A fireproof formwork 2 is integratedly stuck on the outer face of a steel plate 1, and the respective steel plates 1 are arranged outside the pillar main reinforcement 24. Next, the connecting parts 1a of both end parts of the steel plate 1 is connected with the reinforcing plate 3 fixedly secured to the adjoining steelwork beam 22 through a plurality of connecting bolts 5, and concrete C is placed in the connected part. Consequently, the steel plate 1 and the fireproof formwork 2 are formed into a buried formwork, and hence the construction process can remarkably be simplified.