PURPOSE: To reduce the generation of vibrations in continuous plural roil pairs by changing the natural frequency of one roll pair to the other roll pair.

CONSTITUTION: Natural frequencies of continuous plural roll pairs which are directly connected in the running direction of a web and guide the web between gaps are set to be different each other. Even if accidental vibrations of a first roll pair are produced, a second roll pair is not affected by any driving action, and vibrations in the second roll pair which are brought about by slight vibrations of the first roll pair are not developed into rocks owing to a resonance excitation.