PURPOSE: To make the action schedule of entire binding head including a band bonding optionally changeable and selectable, and easily and simply perform maintenance of parts of the binding head by providing a heating plate welding mechanism by which a heating plate is smoothly, certainly inserted in between bands to be bonded and the faces of the bands are adequately pressed on to the heating plate and the molten bands are firmly press-bonded.

CONSTITUTION: A heating plate welding mechanism 20 of a welding mechanism 10 has a cylinder capable of alternatively performing weak pressing in which a piston is pushed out by a spring and strong pressing by compressed air, so that bands are brought in close contact with a heating plate 21 to melt them, and certainly press- bonded by strongly pressing them after the heating plate 21 is removed. A band separating guide and a band guide cylinder 24 are provided to insert the heating plate 21, and the band separating guide 23 is retracted as the heating plate 21 moves forward and the heating plate 21 and the band separating guide 23 move between the bands to be bonded so that the heating plate 21 is smoothly, certainly inserted. A sequential circuit and a solenoid valve are employed as a controller and a grip mechanism is composed of the lower face of a fixed cutter of a shear mechanism and an openable gripper.