To solve the problem that, in pickling treatment where a steel strip is successively passed through a plurality of pickling tanks divided by a cascade gate, the sticking and movement of an acid liquid to the steel strip which is a phenomenon that the acid liquid is stuck to the surface of the steel strip and is brought from a pickling tank in the prestage to a pickling tank in the poststage is made remarkable together with the progression of the wear of the tip part in the cascade gate (caused by the sliding contact with the steel strip), and the balance of the acid concentration/liquid temperature in the pickling tanks is lost and pickling efficiency is damaged, and to suppress the movement of the acid liquid over a long period.

Directly above a cascade gate 1, a steel strip suppression roll 2 having a barrel part composed of a large-sized barrel part 21A and small-sized barrel parts 21B is arrange so as to be freely capable of idle-rotation and is carried on the steel strip. Even if a wear groove 11 is produced at the tip of the cascade gate, the steel strip S passes through the tip of the gate in a state of being inserted between the large-sized barrel part and the bottom face of the wear groove. Thus, the effect of suppressing the sticking and movement of an acid liquid to the steel strip can be maintained over a long period even if the wear of the tip part in the gate progresses, and pickling operation can be efficiently performed.