To prevent squeezing and meandering of a strip which are apt to occur at the time of contact between a rolling material and rolling rolls, and to improve productivity, by eliminating a positional deviation of both ends of rolling rolls during roll gap closing with comparatively simple and inexpensive system in a hydraulic reduction apparatus by tuning cylinder method.

A hydraulic circuit A, which executes roll gap closing of a roll 3 in horizontal state by applying even amount of hydraulic oil through a tuning cylinder 11 to each of a pair of hydraulic reduction cylinders 4a, 4b installed at roll chocks of both ends of the roll 3 of the rolling mill, is accompanied by a correction hydraulic pressure circuit B with a proportional electromagnetic flow control valve 31, which continuously detects positional deviation of the roll chocks at both ends of the rolls during roll gap closing by position sensors 5a, 5b eliminates uneven contact of roll 3 by supplying a compensative amount of hydraulic oil to correct positional deviation to the pair of hydraulic reduction cylinders 4a, 4b.