股東與管理者之間存在著負債融資不足的代理問題。基於較低的融資成本與股權稀釋問題的考量，股東較傾向於負債融資。然而，過多的負債不僅會降低管理者的決策彈性與控制權，也會帶來較高的財務風險，進而威脅到管理者的個人財富與工作保障，管理者因而會避免使用負債。本研究以1997~2006年台灣上市櫃公司為研究樣本，探討股權結構（包括董監事會、大股東、機構投資人與金融機構持股比率高低）對公司負債水準的影響；亦即，驗證董監事、大股東、機構投資人與金融機構是否具有誘因、能力與權力發揮監督功能，提高管理者使用負債的意願，以減緩負債融資不足的代理問題。研究結果顯示董監事、大股東與金融機構持股比率與負債呈現顯著正相關，而機構投資人持股比率負債則呈現顯著負相關。

Shareholders may prefer debt financing owing to its lower costs and the problem of ownership dilution. However, protective covenants and monitoring devices asserted by debt holders may reduce managers' decision-making control and flexibility. Additionally, higher debt indicates greater financial risk. Accordingly, managers who fear of losing control and flexibility and for job and financial security concerns tend to assume small amounts of debt. The agency conflicts between managers and shareholders thus may occur. Using a data set of 1,321 Taiwanese listed firms during the period of 1997~2006, this paper investigates the effect of ownership structure on debt ratio. The empirical results indicate that board shareholding, blockholder shareholding and bank shareholding are positively and significantly associated with debt ratio, suggesting that board of directors, blockholders and banks can serve as an effective governance mechanism. Additionally, institution shareholding is negatively and significantly related to debt ratio, implying that institutions do not help mitigate the under-levered agency problem between shareholders and managers.