To hold initially set tension constant by providing a torque brake that can set torque threshold value to reaction of tension.

As a hard copper wire 6 wound on a conductor delivery bobbin 5 is gradually delivered, the residual quantity of the hard copper wire is reduced, and when the wound diameter becomes small, delivery angular velocity is increased, and reaction of tension of the hard copper wire 6 reaches the set value of a torque brake or more. As a result, a conductor delivery tension device starts rotating, and thereafter follow-up rotation is continued with specified torque until there is no more hard copper wire 6, that is, the conductor delivery tension device rotates automatically following the increase of the delivery angular velocity ω1 of the hard copper wire 6 so as to maintain constant difference ω1-ω2 between the delivery angular velocity ω1 of the hard copper wire 6 and the angular velocity ω2 of the conductor delivery tension device. The hard copper wire can therefore be delivered with constant tension.