公司治理與審計品質同為監督企業之職能，其間可能存在相互影響之關係。本文透過檢測「抑減代理成本」與「提升企業績效」兩方面，驗證公司治理與審計品質各自對於企業之影響，以及公司治理與審計品質是否能先控制代理問題後再有效提升績效，亦或於其監督強度已削減於抑減代理成本之路徑上，使監督職能無法擴展於提升企業之績效；再者，觀察同為監督機制之公司治理與審計品質之相互影響，對於企業代理成本與績效之效果是否產生改變。研究結果顯示，公司治理能有效抑制代理成本後再提升企業績效；而審計品質在抑減代理成本之效果上卻未獲得支持，且同為監督機制之公司治理與審計品質存在正向之相互影響。具體而言，本研究的主要結果如下：(1) 審計品質於查核財報可靠性之外的附加價值；(2) 公司治理與審計品質在抑減代理成本及提升企業績效之功能上是否能同時發揮；(3) 公司治理與審計品質存在交互影響，是否能透過對方之影響後再對企業產生作用；(4) 透過結構方程模式之分析，克服使用單一觀察變數造成研究結果分析之限制並提供路徑分析之檢測。 Corporate governance and audit quality are regarded as supervisory mechanisms for a company; as such, a mutual effect can exist between the two mechanisms. This study uses two aspects (suppressing agency costs and improving company performance) to examine the individual effects of corporate governance and audit quality towards a company. Corporate governance and audit quality are examined to see whether they can first control for agency problem and then improve performance; or whether the supervisory strengths of corporate governance and audit quality have already been expended on the path to suppressing agency costs, thus, making the supervisory mechanisms unable to further improve company performance. Furthermore, the corporate governance and audit quality mutual effects are investigated to see their produced changes on agency costs and company performance. The results indicate that corporate governance can effectively suppress agency costs and then increase company performance, while audit quality has no significant suppressing effects on agency costs; in addition, there exists a positive mutual effect for both supervisory corporate governance and audit quality mechanisms. The results of this study wishes to contribute to the literature through understanding (1) the added value, aside from reliability, of audit quality on checking financial statements, (2) whether the simultaneous effects of corporate governance and audit quality on suppressing agency costs and increasing company performance can be observed, (3) the existence of corporate governance and audit quality mutual effects, and whether the mutual effects between these two can produce changes on the company, and (4) the use of structural equation modeling analysis in overcoming the research results analysis limitations of using a single observed variable, and the performance of path analyses testing.