A production system for producing products from raw materials by a production process with several steps has a number of production facilities that perform the steps and a control device. The control device determines a control target value by referring to information about group combinations specified in accordance with the relative merits of the manufacturing condition routes followed by respective lots during the production process. The relative merits are determined on the basis of quality items of the lots, classified for inter-step combinations of groups, which are classified on the basis of manufacturing conditions at the steps.