PURPOSE: To mechanically perform a prework to bind reinforcing bars by means of a wire and a work to twist and bind both end parts of the wire by providing a needle holding means, a needle feed part to feed a wire to a curling means, and a drive part to exert twist deformation on the held wire.

CONSTITUTION: A curling mechanism is driven with the aid of a motor to extrude a wire 4 in a circular shape, and the tip is moved around to the back of an intersection point between reinforcing bars. The wire is guided to a slope and a wire guide 14 and passes through a position above a clamp rest 9, and the wire 8 is extruded from the clamp rest 9 by a given size. A clamp 11 is operated with the aid of a motor, and the tip of the wire 8 is pressed against the clamp rest 9. Thereafter, the whole of a reinforcing bar binder is pulled this side, and the wire 8 is pulled toward an intersection point between crossing reinforcing bars. After the wire 8 is placed in a wire groove 24 of a fork 18 of a twist head 2, the wire 8 is cut by means of a cutter 12. The twist head 2 capturing the wire 8 is rotated with the aid of the motor, the wire 8 is twisted, and the reinforcing bars are tightly bound by means of the wire 8.