ISO 9000 is a series of several standards(ISO 8402, 9000, 9001, 9002, 9003, 9004,...). ISO 9000 is a standard explaining fundamental concepts, defining important terms, and providing guidance for selecting among the other standards. ISO 9001, the most comprehensive standard to ensure quality in design, development, production, installation, and servicing. ISO 9002 is used to assure conformance to specification, installation and servicing. ISO 9003 has the least requirement among three standards and applies to inspection and final testing. ISO 9004 is a standard developed for internal use only and not applicabe to contractual arrangements. In this paper, quality system requirements for ISO 9000 series are also specified.