PURPOSE: To facilitate an operation at the time of tension control and to prevent the occurrence of a paper break, etc., through erroneous setting by equipping a tension detector, a determination circuit for determining a variation of tension, a tension increase commander for commanding a tension increase, a tension decrease commander for commanding a tension decrease, a comparison circuit, an integration circuit and a correction quantity calculation circuit.

CONSTITUTION: When an operator manipulates a tension-ON commander 8, a real tension signal is inputted to a tension setting circuit 10. The tension setting circuit 10 outputs the real tension signal as the set point signal of tension to a comparison circuit 13. When the increase of the set point of tension is desired after a tension control is ON, a tension increase commander 11 is operated to input a tension increase command to the tension setting circuit 10. The tension setting circuit 10 increase the set point of tension in proportion to the period of time, during which the tension increase command is inputted, to input the tension set point signal to the comparison circuit 13. When the decrease of the tension set point is desired after the tension control is ON, a tension decrease commander 12 is operated to input a tension decrease command to the tension setting circuit 10. The tension setting circuit 10 decreases the set point of tension in proportion to the period of time, during which the tension decrease command is inputted, to input the tension set point signal to the comparison circuit 13.