This study deals with a case analysis about equity valuation of green growth industry in Korea. Green growth is a way to synergize economic growth and environmental protection, and internationally it is highlighted as a potential developing industry for new era. In recent years, Korean government also has an attention to green growth and begins to emphasize the importance of green growth. Many new polices about green growth are announced and many new firms in green growth industry are established. Therefore, understanding of green growth is very essential for adapting to the new surroundings in this time. For your understanding of green growth, we provide the definition and trend in Korea of green growth. Further, we suggest practical examples of Millinet Solar and GS fuelcell. Both firms are currently existing firms in Korean green growth industry. We will introduce their market and firm circumstance and eventually valuate their firm-value using the Residual Operating Income (ReOI) valuation model. Preferentially, we begin to explain the theoretical background of ReOI valuation model which is derived from Ohlson (1995) and its implemental framework before presenting about green growth because this prior explanation about the valuation model will be helpful to understand the practical firm examples later effectively. Basically, ReOI valuation model focuses on operating income but ignores the effect of financial activity since residual income is created by operating activity. We will explain how to assort operating activity and financial activity from balance sheet and income statement for reformulating financial statements. After the explanation of the valuation model, we provide definition of green growth, encouraging green growth policies in Korea, market and firm analysis, and eventually valuate the value of two existing green growth firms using ReOI valuation model. Although there are many theoretical and empirical research papers regarding equity valuation, there is no specific case analysis report for the practical implementation of ReOI valuation model for Korean green growth companies. This case study aims to fill this void in the academic literature. This case study may contribute to both industry and academic communities by describing how to implement theoretical valuation model in practice.