Prior researches of the firm value primarily focus on the governance structure and financial conditions of firms. In detail, empirical topic of prior researches are summarized as follows: First researches of governance structure focus the comparative analysis of the firm value to the change of stockholders’ share ratio(inside ownership, foreign ownership and institutional ownership). Additionally they investigate empirically for the effect how outside directors on the board of directors and audit committee can cause the firm value. Second researches of financial conditions examine empirically the relationship between the firm size, the debt constraint, the accounting performance and development expenditures and it’s effect on the firm value. In conclusion, prior researches show that the governance structure and financial conditions of firms significantly effects on the firm value. But up to the present there is no study empirically to examine the effect how the audit quality as manager’s inside/outside monitor can cause the firm value. Thus examining the monitoring role of the audit quality and the exploring the relation between the audit quality and firm value is clearly an interesting and important research topic. Particularly after the effect of the Korean monetary crisis in 1997, the independence and expertise of auditors monitoring the accounting information has been emphasizing in Korea. So that this paper examines whether market participants evaluate the firm value differentially depending on the audit quality. Exactly we investigate empirically whether the existence of high quality audits enhances firm value in Korea. Specifically we predict that the higher the audit quality is, the higher the firm value is. Because auditors with high quality can throughly monitor and control the managerial actions of managers, firms with high quality audits can provide the more reliable information to market participants and reduce agency costs. But auditors with low quality can easily acquiesce to auditee pressure, including pressure to allow earnings management. So this will lead to a difference in the firm value between firms with high quality audits and firms with low quality audits. But it is very difficult directly to estimate the audit quality. So in this paper we respectively use auditor size(Big five or Nonbig five auditors depending on the affiliation with foreign Big five audit firms: Big five auditors are known as those having higher reputation and audit quality), audit services time and audit services fees as a surrogate for the audit quality according to prior research. And we use Tobin’s Q ratio as a proxy for the firm value. The sample consists of non-banking firms(2,013 firm-years) with December fiscal year listed in Korean Stock Exchange over 1999-2003. Consistent with the prediction, we find that the higher the audit quality is, the more increases the firm value represented as Tobin’s Q in the Korean stock market. More specifically, our results of empirical test are as follows: (1) The difference in firm value significantly exists between Big five auditees and Nonbig five auditees. Firm value is higher for firms that are audited by high-quality auditors(Big five auditors) than for those that are audited by low-quality auditors(Nonbig five auditors). (2) There is significant positive association between the firm value and an amount of audit services time. Firm value is high as an amount of audit services time increases. (3) There is also significant positive association between the firm value and an amount of audit services fees. Firm value is higher for firms that pay the more audit services fees to auditors. Such associations remain robust even after we include various control variables(governance mechanism and financial conditions) that may explain firm value. Additionally, we examine whether or not high-Tobin’s Q firms hire high quality audits(Big five auditors) to signal a favorable information. But there is no evidence that high-Tobin’s Q firms hire high quality audits. So we conclude that high quality auditors as manager’s inside/outside monitor can enhance firm value. These results indicate that the audit quality is important factor when market participants evaluate the firm value. So it is necessary to make efforts to enhance and encourage audit quality in the Korean accounting and audit industry for improvement of the firm value.