Belt-loops are fed out by the conventional gear-roller feeding mechanism and also drawn out by the new drawing mechanism on the clamp device. Supported by these two mechanisms, the folding fork catches “curled” or “creased” belt-loops every time and supplies them to the head. In addition, the sensor of the clamp device detects the presence/absence of belt-loops. If it detects a faulty belt-loop feed, the clamp device automatically repeats the clamping action. Since the operator doesn't have to operate the set-back switch, less time is lost.