In this paper, we analyse empirically the relations between ownership structure and capital structure of firms listed on Korea Securities Market and Kosdaq Market of Korea Exchange. The main results of this study can be summarized as follows. Debt ratio decrease as large shareholder' equity holdings increase. Debt ratio decrease as the difference between first largest shareholder's and second largest shareholder's equity holdings increase, and Debt ratio decrease as the ownership concentration increase. Managerial ownership exert a non-linear effects on capital structure. So to speak, at lower level of managerial ownership managers hold lower level of debt to pursue their own interests at the expense of minority shareholders, but at higher level of managerial ownership the interests of managers and shareholders are aligned. Therefore, indicate a non-linear U-shaped relation between level of managerial ownership managers and leverage. Debt ratio decrease larger in owner-controlled firm than in management-controlled firm. These results support the expropriation of minority shareholders hypothesis that large shareholders can extract private benefits from corporate resources under their control at the expense of minority shareholders. This paper contributes to defining information value of large shareholder's equity holdings and managerial ownership on capital structure for a firms' other stakeholders such as investors and creditors, and to strengthening a legal and institutional safeguard for external minority shareholders. Ownership concentration might have negatively affected the evolution of the legal and institutional frameworks for corporate governance and the manner in which economic activity is conducted. It could be a formidable barrier to future policy reform.