PURPOSE: To coil without loosing and to produce the thin flat bar with good quality by absorbing the variation of the length generated at the time when the thin sheet is slit at multi positions at the same time with the tension roller.

CONSTITUTION: The fixed position tension roller 4a and the movable tension roller 4b are arranged in zigzag with alternately changed height. The presser roller 6 is arranged against the roller 4a, presses the flat bar 5 to the roller 4a, prevents from slipping and gives the tension surely. The roller 4a has a shaft 9, on the shaft 9 the rollers 10 of which outer periphery is made of elastic member are supported freely, bendably through bearing 11 by the number corresponding to the number of the flat bars. Accordingly, if there is a flat bar with long or short caused on the variation of thickness among them, the respective roller bodies change the rotary speed relatively and every flat bar is coiled under applied with the almost same tension between the coiling device and the tension device.