To improve reliability in the welding of coil-binding band by providing a welding head with a sensor for detecting the set position of a face gate and by adjusting according to the detection a path for the passage of the binding band so that it is within a specific size.

An upper sensor 51 comprising a light source 52 and a light- receiving device 53 is disposed in the upper bound of the permissible zone of a face gate 10 positioned in the welding head 5 of a binder-band-binding device and used for guiding the leading end of binder band into the welding head 5, and a lower sensor 54 comprising a light source 55 and a light-receiving device 56 is set in the lower boundary of the permissible zone. Through-holes 61 and 62 made through the right and left of the welding head 5 are provided so that the light-receiving devices 53 and 56 sense light from the light sources 52 and 55 passed through the through-holes 61 and 62. Thus, when the upper sensor 51 is on and the lower sensor 54 is off, the device judges that the face gate 10 is in a normal set position.