To provide an adjusting method for a light reduction zone in a continuous casting facility and an adjusting mechanism for the light reduction zone by which even in the case of shifting the light reduction zone while continuing a casting work, the development of crack and strain in a cast slab can be prevented.

In the method of adjusting the position of the light reduction zone A in the continuous casting facility, in the light reduction zone A, the adjustment of a distance and a gradient of tiltable frame 11 to a reference frame 12 in each guide roll segment S, are adjusted in order from the upstream side guide roll segment S toward the downstream side guide roll segment S. At mutually faced end parts of the adjacent guide roll segments S, the difference of the distance between the reference frame 12 and the tiltable frame 11 at the end part of one of the guide roll segment S and the distance between the reference frame 12 and the tiltable frame 11 at the end part of the other guide roll segment S, is made to 0-0.5 mm.