To control the tension to be constant even when the brake characteristic is changed by detecting the load of a motor to drive a bridle roll installed rearward of an un-coiler, and changing the air brake pressure of the un-coiler.

A coil 1 held by a drum 2 is carried to a rear equipment 6 through a bridle roll 5. The un-coiling tension FB, is generated between the coil 1 and the bridle roll 5, and the forward tension FF is generated between the equipment 6 and the bridle roll 5. When the un-coiling tension FB and the forward tension FF are changed, the load of a motor 7 to drive the bridle roll 5 is changed. The load of the motor 7 is detected, and the air brake pressure to be fed to a brake element 9 of a drum 2 is changed. The effect of the change in the tension of the rear equipment 6 can also be controlled to keep the tension to be constant with excellent accuracy.