To reduce the operating time of a crane, and to improve operating efficiency by setting a steel-framed beam at an accurate place at a time on a temporary steel frame.

A marking line 12 indicating the place of the installation of H-steel 11 as the steel-framed beam for the unit floor is drawn on a temporary steel frame 10, a positioning jig 1 manufactured by a steel plate piece 3 and an angle 2 is fixed temporarily on the temporary steel frame 10 in conformity with the marking line 12, and H-steel 11 is suspended by a crane, and applied to the positioning jig 1 and positioned on the temporary steel frame 10.