This thesis is to research for analysis of ISO 9000 Quality Management System application status of small & medium-sized Industrial Companies. For this research, 10 companies certified by ISO 9000 standard were selected. By using an evaluation method and a software for analysis of application, this thesis compared, analyzed and evaluated the application status before and after certificate of ISO 9000, and identified the performance and difficulty of QMS application, and then proposed improvement methodology for ISO 9000 effective application.