PURPOSE: To control an adequate pickling speed by correcting the set speed of a steel strip in accordance with the total value of the respective catenary heights in plural pickling tanks in which the steel strip passes successively and the distance between the peaks of the catenaries and the tank bottoms.

CONSTITUTION: The steel strip 2 is run at a prescribed speed by bridle rolls 4, 5 and is successively passed in the plural pickling tanks 1, by which the catenaries are formed in acid solns. and the surface scale is removed. The catenary heights h1, h2...hn in the respective pickling tanks 1 of the above-mentioned pickling equipment are measured and the total value H thereof is determined. The total immersion length is determined from this total value H in an arithmetic circuit 13 and the speed correction quantity is calculated in an arithmetic circuit 91 from the deviation from the set value of the total immersion length. The speed set value corresponding to the set value of the above-mentioned total immersion length is corrected in accordance with this correction quantity. Further, the distance (y) between the catenary peak part and the tank bottom is measured by a magnet type steel strip detector 3 and the prescribed speed set value is corrected in accordance therewith. The pickling speed of the steel strip 2 is controlled via automatic speed controllers 43, 53 in accordance with the above- mentioned correction value.