To improve the workability by providing an anchor hole in a joint part for pillar, and inserting each anchor of a gusset plate in the anchor hole from right and left for setting, and installing a stretch member provided with a pin hole and a slit.

An anchor hole 9 is horizontally provided in a joint part of a pillar 7. A gusset plate with anchor provided with a male screw 2 and an anchor 4 of a gusset plate with anchor provided with a female screw 3 are inserted into the anchor hole 9 from right and left for setting. A stretch member 8 provided with a pin ball 6 and a slit 10 in a joint part thereof is installed in the gusset plate 1, and joined by a drift pin 11. A seal 13 is attached to the outer surfaces of the pillar 7 and the stretch member 8. Adhesive agent 12 is filled from an upper part of the slit 10 so as to fix the outer surfaces of the anchor 4 and the gusset plate 1 and the inner surfaces of the anchor hole 9 and the slit 10. With this structure, bending stress and shearing stress of the stretch member 8 can be transmitted to the pillar 7, and furthermore, workability and safety can be improved.