In the first report, we proposed a method of optimum design using fuzzy numbers as design variables. But in that report, all the calculations had been performed by a basic fuzzy number operator, so the problems to be solved are restricted only those whose equations are expressed explicitly. As most of the optimum design problems are not so simple, especially in structural design problems, it will be rather difficult and sometimes almost impossible to express the equations such as objective function and constraints explicitly. For this reason, we developed a simple fuzzy number operation and examined its adequacy through comparison with the basic fuzzy operation. In this report, we solve the same optimum design problem which was solved in the first report, and examined the efficiency of the method. We then apply it to the optimum design problem on the lib structure of a parabolic antenna, and we examine and show the effectiveness of the method.