This study examines the effects of ISO 9001:2000 Quality Management System(QMS). Before accrediting it, it is affected by the top management leadership and corporate culture. After finishing the accreditation, some companies form quality culture, but some companies do not. That affects the corporate performance. If quality culture forms, companies performance will be good. But if not, companies performance will be bad. The accreditation of ISO QMS is not the end goal for the companies but forming the quality culture will enhance the corporate performance.