PURPOSE: To rapidly, easily and quantitatively judge the thickness of a metallic sheet by comparing the predicted value of the thickness precision with the tolerance of the product to judge the acceptance or unacceptability of the sheet thickness of the sheet at the time point when the hot rolling is completed.

CONSTITUTION: The metallic sheet P is rolled in the hot rolling process 1 and coiled around a hot coil HC. This sheet is rolled in the cold rolling process 2. The cold rolled sheet precision change model and the profile change model 24, 25 to be prepared by the statistical analysis of the experiences of the change in the cold rolling of the thickness precision are prepared. Based on the experiences of the thickness and the profile of the metallic sheet to be obtained at the time point when the hot rolling is completed, the thickness precision of the metallic sheet after the cold rolling is predicted using the respective models 24, 25 by a comprehensive thickness precision calculation and acceptance/ unacceptability judging part 26, etc. This predicted value is compared with the product tolerance 42 to judge the acceptance/unacceptability of the thickness of the metallic sheet or bar. The evaluation of the thickness precision model and the validity of the judgement of the hot rolled sheet thickness using this model can be quantitatively grasped.