I investigate whether the efficient ratios used as the proxies of the agency costs maintained by Ang et al.(2000) is significant. Utilizing a sample of 77 manufacturing companies listed on the KOSDAQ from the TS2000 of the KSDA, The results are as follows. Agency costs are found to be decreasing with the ownership share of controlling shareholders and accounting performance becomes higher. But firm value measured by Tobin's Q ratio becomes lower according as the ownership of the controlling shareholders increases. If agency costs decrease in proportion to controlling shareholder's share, firm value should be higher according to the agency theory by Jensen and Meckling(I976). But the results of the empirical test of this study are inconsistent with Jensen and Meckling's(1976). Therefore the following study on the more useful proxies stand for agency costs should be needed