A thickness control means

A high-precision plate thickness controlling device capable of controlling a variation component that cannot be analyzed by frequency analysis, requiring no plate thickness gauge and causing no reduction in accuracy due to a tracking error. A plate thickness controlling device which controls a plate thickness variation produced in association with the rotation position of a rolling roll or a support roll assembled in a roll stand for rolling a metal material and caused by roll eccentricity or the like, and which is characterized by comprising a rolling force variation calculating means for calculating the variation component of rolling force produced in association with the rotation position of the roll from the rolling forces and the rotation positions of the rolls and adding/recording the calculated variation component of rolling force for each rotation position of the roll, a controlled variable computing means for computing a rolling roll gap instruction value that can reduce a plate thickness variation using a variation component of rolling force for each rotation position of the roll provided by the rolling force variation calculating means and outputting a rolling roll gap instruction value at timing selected according to the rotation of the roll, and a roll gap operating means for operating the rolling roll gap of the roll stand based on a rolling roll gap instruction value from the controlled variable computing means.