In the 21st century, The service industry is becoming a new core business. In the modern industrial society, it escapes from supporting the manufacturing industry and finally leads to the growth of the manufacturing industry. Although many companies have met a variety of customer requirements through the existing service process, an organization or service developer has been failed because they had depended on intuitive judgment. Therefore, in this paper, we suggests CSIM(Case-based Service Improvement Methodology) to support improvement direction. This methodology is based on 120 cases and developed by utilizing the TRIZ concepts. As a result, CSIM will be a creative tool to support a developer to solve the problems.