PURPOSE: To join a large beam without the need for an adjustment of length thereof that may be reguired by construction error in interval between columns by forming the large beam so that a clearance is formed between the large beam and a main permanent sub-structural column and joining the large beam on the side of the clearance by means of bolts.

CONSTITUTION: A large beam 2 is made smaller in length so as to provide a clearance 8 between the beam 2 and the side surface of a permanent sub- structural column 1. A joining plate 9, from which a gusset plate 10 projects so as to overlap a gusset plate 7 on the side surface of the permanent sub- structural column 1, is provided on one end surface of the large beam 2. The other end of the beam is welded to the column. One end of the beam 2 spaced from the side of the column by the clrearance 8 is joined to the column by means of a high-tension bolt 14 provided between the plate 9 and a column flange and a bolt 15 inserted through both of the gusset plates 7, 10. Cement compositions are filled into the clearance 8 to join the permanent sub-structural column 1 integrally to the beam 2.