PURPOSE: To reduce the kinds of doubling plates and besides, enlarge the strength of a junction by bolts.

CONSTITUTION: Splice plates 3 are annexed astride the abutment to the external surfaces of both flanges 2 of a pillar or a beam 1 consisting of H-type steels butted in the shape of a straight line, and besides doubling angle plates 5 are annexed to the faces in L shape consisting of each inner face of both flanges and the side faces of webs 4, while the flange abutments 5a of both splice plates and each doubling plate are fastened to the flanges with plural bolts and nuts 6. Besides, the web abutments part 5b of each doubling angle plate are fastened to the web by plural bolts and nuts. Hereby, the kinds of doubling plates become two, and the doubling angle plate bears both the bending moment and the shearing force.