To provide an assembling device of a brace safely, rapidly assembling the brace generally used as a bracing such as a building structure, a temporary frame base or the like.

In an assembling device of the brace by which screws of two bolt ends are respectively screwed in screw holes having mutually different screw directions, formed at both ends of a cylindrical turn buckle to build up a brace, a turnbuckle support 7 having a drive means rotating the turnbuckle for screwing the bolt in the screw hole of the turnbuckle around the shaft of the cylinder and a bolt support 8 supporting the pair of bolts irrotationally and to be straightly transferable toward the turnbuckle are provided. Further, the bolt support 8 is provided with an adjusting means positioning the center of the bolt screw in the center of the screw hole of the turnbuckle and urges the bolt to the turnbuckle.