PURPOSE: To shorten the suspension time of a crane when a reinforced cage for a column is built.

CONSTITUTION: Building jigs 50 are set previously to the screw reinforcing bars 21 of a concrete structure. Slits 54, 55 are formed in the lower-side horizontal plate sections and upper-side horizontal plate sections of the building jigs 50 respectively. The horizontal plate sections are held and bone by coupler nuts 30 and first locknuts 31 screwed to the screw reinforcing bars 21 under the state that the screw reinforcing bars 21 are stored in the slits 54 of the lower-side horizontal plate sections. A reinforced cage 10 for a column is hung down by a crane 100, the screw reinforcing bars 11 of the reinforced cage 10 are passed through the slits 55 of the upper-side horizontal plate sections, previously screwed second locknuts 32 are placed on the upper-side horizontal plates, and the reinforced cage 10 for the column is self-supported. The suspended state by the crane is released, the screw reinforcing bars 11, 21 are connected by the coupler nuts 30, the building jigs 50 are extracted, and both locknuts 31, 32 are clamped to the coupler nuts 30.