本研究檢驗台灣股票市場本國機構投資人與外國機構投資人的持股，能否作為一種潛在機制對於其持股公司的資本結構產生影響。我們以三大法人：投信、自營商，與外資作為研究對象。研究結果顯示，外資持股對公司負債比率的影響為反向，但本國機構投資人對於公司負債比率的影響卻為正向，又以投信的效果更為顯著。由於外資持股與本國機構持股並未呈現明顯的替代關係，故兩者對於公司資本結構所具有的對立影響可視為兩個獨立效果。由於現存文獻對此並未著墨，本研究認為在解讀不同類型機構投資人的持股資訊時，需以不同觀點來思考。一方面，外資可能較重視公司的財務風險，故會導致公司採取較低的負債比率以降低違約風險；另一方面，本國機構投資人可能偏好公司能提供較高的股東權益報酬率，故導致公司採用低股權高負債的資本結構以避免稀釋盈餘。

The purpose of this paper is to examine the relationship between three major institutional holdings and firm capital structures on the Taiwan stock market, thereby exploring whether institutional holdings can influence capital structures. The results show that among three institutional investors, foreign institutional holding can affect the firm's capital structure most. As the foreign institutional holding increases, the leverage ratio decreases. Conversely, domestic institutional holding positively affects the firm's capital structure, especially for the Investment and Trust. In existing literature, there are few studies about this topic yet; therefore, this study can shed new light on the association between institutional holding, particularly for foreign institutions, and the firm's capital structure. We also realize that different institutional investors may prefer different firm characteristics. Moreover, this study presents that how institutional investors can affect a firm's capital structure through the market mechanism.