PURPOSE: To have accurate control of reel tension, in a rolling plant etc. for band-shaped material, by carrying out the control while an acceleration/deceleration compensating portion to the tension setting current, and by suppressing the torque variation owing to change of the coil diameter.

CONSTITUTION: In this measuring device 5, the coil dia. is determined from line speed V and the number of revolutions of motor, N, and the acceleration/deceleration signal from a differentiation device 7 is multiplied with a function F(D) calculated by an operator 6. The portion of compensation for acceleration/deceleration is added to the current Iref for setting the reel tension so as to control the motor for winding/rewinding with the aid of a current controller 10. Besides this control system, a reel dia. change compensator circuit 14 is furnished, in which the function F(D) of above-mentioned operator 6 is multiplied with the product of outputs from a plate thickness factor circuit 12 for thickness h of the material and a square calculation circuit 11 for number of revolutions N, and this product obtained is subtracted from the current value Iref. According to this arrangement, the reel tension can be controlled with high precision whether the line is in accelerative or decelerative operation or in constant speed operation.