Shareholder activism in public pension funds, asset management firms, and foreign hedge funds have led to an increasing number of calls for dividend payouts, so listed firms on the Korean Stock Exchange should urgently prepare an optimal dividend policy for raising corporate value in the mid- to long-term. However, developing such a policy has not previously been discussed or analyzed. In this study a method of deriving the optimal dividend policy of a firm to maximize its value is suggested. Based on the arguments (Fama and Babiak, 1968; Marsh and Merton, 1987; Lee, 1996, etc.) that cash dividends rely on permanent earnings and on the empirical findings (Fama and French, 1998; Pinkowitz, Stulz, and Williamson, 2006 and etc.) that cash dividends contribute to an increase in corporate value, the effect of cash dividends, which are driven by the permanence of earnings, on corporate values is analyzed. In the Beveridge-Nelson method earnings are divided into permanent and temporary earnings. Empirical results show that as the proportion of cash dividend relative to permanent earnings increases, corporate value increases significantly. Second, it is possible to derive the optimal level of dividend for a company, as the proportion of cash dividend relative to the permanent earnings is nonlinear and takes a reverse U form. Specifically, we find that corporate value increases with the cash dividend proportion of permanent earnings up to the point of 41.47%, and it decreases as the percentage increases beyond this point. These results imply that domestic firms must realize their optimal dividend policy by considering the persistence of earnings, and that institutional investors need to monitor whether a firm's dividend policy at a micro level is aimed at achieving its optimal dividend level, which can maximize its shareholder value.