A design variable optimization system including a performance value calculating section for performing an analysis on a design article using numerous design variables and for calculating a performance value for evaluating the performance of the design article using each of the design variables, based on the result of analysis. A design variable determining section is provided for determining an optimal design variable among the design variables, based on each of performance values calculated by the performance value calculating section and a certain evaluation criterion. An analysis end time determining section is provided for determining an end time of the analysis in the performance value calculating section so that a difference between an end time of a period necessary for the calculation of the performance value and the end time of the analysis becomes a predetermined, fixed value.