Abstract: A production instruction volume decision support method comprising the steps of: creating a plurality of sets of amount of the production order; obtaining a plurality of evaluation values based on simulation of demand for each product; obtaining a superiority relationship among the sets of amount of the production order from the evaluation values; creating a new set of amount of the production order from two sets of amount of the production order which are superior to the other sets of amount of the production order; repeating the above steps a predetermined number of times to obtain solutions to the plurality of sets of amount of the production order which have been optimized; displaying a plurality of sets of amount of the production order which have nothing superior thereto; and enabling a user to select one of them according to his/her management policy.