[Purpose] In Korean listed companies, we check whether corporate value decreases as the major shareholder’s equity ratio increases, and whether it can be used as an improvement measure to ultimately increase corporate value by reducing agency costs by improving corporate governance in ESG when the majority shareholder’s equity ratio increases. It is necessary to conduct an empirical analysis. [Methodology] As major independent variables, the major shareholder’s equity ratio and the Korea ESG Standards Institute’s five corporate governance variables (total score, shareholder rights protection, board of directors, disclosure, audit organization) were used. [Findings] Through this study, it was empirically confirmed that corporate value decreases as the majority shareholder’s shareholding ratio increases, and that companies with excellent corporate governance increase corporate value by reducing agency costs. However, the board of directors variable, which is part of the five corporate governance variables, was found to have the greatest moderating effect, and the remaining variables did not show a significant moderating effect. [Implications] This study suggests that if company’s stakeholders intensively monitor the board of directors, they can increase corporate value by reducing agency costs between majority and minority shareholders.