It is widely recognized that ISO 9000 certification bring some profits, such as enhancement of quality system and some concerns. Since one of the major concerns is cost for certification, this paper considers the cost for ISO 9000 certification in Japanese companies through review some winning reports and case studies. Specifically, a model that describes the certification activities and their cost is derived through reviewing some winning reports in order to give a framework of cost estimation. Based on the model, we estimate the certification cost in an electric division of a company through an interview survey. Furthermore, we focused on the cost for promotion and administration as a cost for the sake only certification, because these activities will not be needed if a company does not implement ISO certification. It is concluded that this cost may vary approximately 300,000-700,000 (US$) per certification by the interview and telephone surveys to Japanese steel companies.