PURPOSE: To conform the residual length of a rolling material coiled on an unwinding reel after completion of deceleration nearly with the target length by providing a deceleration ratio adjusting device to adjust the deceleration ratio of a speed controller.

CONSTITUTION: The difference L between a sending length L and the residual length LR is calculated based on a carrier speed V and a circumferential length CA continuously after an arithmetic unit outputs a deceleration command 17 and whether the deceleration is executed normally or not is monitored to check the reasonableness. When the relational equation 1 exists, the deceleration is regarded as normal, the deceleration is continued as it is and when it does not exist, the deceleration is regarded as abnormal and the deceleration adjusting device 20 adjusts the deceleration ratio of the speed controller 6. Consequently, the speed controller 6 decelerates rolling rolls 3 with the optimum deceleration ratio and the residual length LR of the rolling material 1 coiled on the unwinding reel 2 after completion of deceleration conforms nearly with the target length.