PURPOSE: To make improvements in workability in site by laying a horizontal member, supporting a form of a column part of a target panel zone, over both upper and lower surfaces of a beam member, and attaching a steel plate doubling as the form of the column part, to the horizontal member free of detachment.

CONSTITUTION: Steel beams 2 by H-sectional material are connected and crossed to a section square steel frame member 1, and a column is of steel framed reinforced concrete structure and the beam is set down to a panel zone of steel framed compound structure. A platelike fixed form 3 orthogonal with a web is welded to both sides of the web of the steel beam 2, and there is provided with a shear reinforcing bar 4, using an L-shaped flat bar made up of bending a band plate at right angles in place of a hoop and the end is welded to the web of the steel frame member 1. Then, horizontal members 5-5a equivalent to a horizontal end thick member pressing a concrete form for a column part related to the panel zone are attached to top and bottom of the steel beam 2. With this constitution, any form work at a building site can be made unnecessary.