To provide a chuck capable of surely grasping a bolt and to readily attach it in connection between beam and square steel pipe column with bolt.

This chuck has a holding portion (1) to screw bolt by threading with a thread (41) of the bolt (4) and wire type guide portion (2), which is connected to edge of holding portion (1) and is longer than width of square steel pipe column. It is preferable that the holding portion (1) be wound as a thread or molded in cylinder with an inner thread, so that a piano wire material or hard synthetic resin which has abrasion resistance and elasticity be used. It is better that the whole length of guide portion (2) have a slight curvature.