A management method is able to quickly investigate the cause of a defect generated in a semiconductor product manufacturing process. Manufacturing conditions in various QFP manufacturing steps are stored in a main server while correlating them with an identification number of the QFP, and a two-dimensional bar code corresponding to the identification number is stamped to the surface of the QFP. In the event of occurrence of a defect of the QFP, the manufacturing conditions for the QFP stored in the main server can be traced in an instant by reading the two-dimensional bar code of the QFP and thereby specifying the identification number.