PURPOSE: To facilitate connecting construction by connecting a connection part fixed on a structure and an unboned brace together by a lap-joint plate through butt connection between H-shape steel sections provided at ends.

CONSTITUTION: A connection part 13 is provided at a connection between a column and a beam of a structure, and an unboned brace 20 is connected and fixed in the diagonal state between the connection parts 13. This unboned brace 20 is constituted by an H-shape steel 21, a concrete 24 slidably covering the H-shape steel 21 and a reinforcing plate 23. Then, the H-shape steel sections 21 of the unboned brace 20 are butt-connected to the connection part 13 and fixed with a bolt by connecting a lapjoint plate to it. Thus, local buckling can be prevented by reducing stress at an end of core steel.