To reduce an angle transmission error caused by a strain wave gear speed reducer.

The output sides of first and second strain wave gear speed reducers connected to individual drive motors are attached to the ends of roll shafts in both ends of a blanket roll and, when the blanket roll is rotated in one direction, the rotational directions of outputs when viewed from the outputs of the respective harmonic speed reducers are relatively reversed. When an angle transmission errors are measured for the respective strain wave gear speed reducers, the waveforms of the respective angle transmission errors are almost reversed in the rotational angle direction of the blanket roll as indicated by a line A and a line B, so that the phases of the respective strain wave gear speed reducers are shifted in such a way that the maximum value 12a and the minimum value 12b of the angle transmission error of one strain wave gear speed reducer overlap the minimum value 13a and the maximum value 13a of the angle transmission error of the other strain wave gear speed reducer. By canceling the angle transmission angle errors of the respective strain wave gear speed reducers each other, fluctuation in angle transmission errors with respect to the blanket roll is reduced.