The purpose of this articls is to investigate the impacts of ISO 14001 certification on the compliance of environmental regulations by Korean companies. The impact of ISO 14001 certification on the industries obtained the certificates was studied through a survey with questionnaires, and the compliance of environmental regulations was investigated using governmental release data. Motivations of Korean companies' environmental management were mostly caused by customer's request and the requirement from foreign countries. Certified enterprises showed more 3 times compliance of environmental regulation than non-certified ones. Such results were accomplished by systematic environmental management such as clear implementation purpose and all employee's voluntary improving according to ISO 14001 requirement. The continuous monitoring system was possible through internal audit and biannual audit from the certification body, to be finally verified by the top management. The four steps in ISO 14001 environmental management system, which are objective, methodology, inspection and monitoring, has contributed to this achievement.