PURPOSE: To obtain a reasonable rolling mill, by providing upper and lower rolls with a speed difference only when threading the mill with a rolling material to form chamber at the front end of the material after running out of the rolls, in a rolling mill which drives separately the upper and lower rolls by different motors.

CONSTITUTION: Motors 6, 7 provided respectively to upper and lower rolling rolls are driven at the speeds VT, VB (VB>VT) corresponding to the set speeds set by a speed setter 13. In this state, when the threading of a rolling material is performed, the front end of the material is bent upward, and simultaneously the currents of motors 6, 7 are rapidly increased. And when the currents exceed set values, a load balancing control is performed, and the speeds VB, VT are made equal to each other to operate a normal rolling.