本文藉由對自由現金流量假說與資訊不對稱假說的驗證，探討資本支出對公司股票報酬的影響。其中，自由現金流量假說主張資本支出增加會使公司股票報酬提高；而資訊不對稱假說則認爲資本支出增加會降低公司股票報酬。我們依循Titman et al. (2004)的研究方法，以台灣上市公司爲研究對象，分別利用特徵調整模型與Fama-French三因子模型，檢驗資本支出與公司股票報酬間的關係。實證結果顯示，資本支出增加對公司股票報酬的影響爲正，偏向資訊不對稱假說的論點，但若只考慮資本支出增加爲正的樣本時，則較偏向自由現金流量假說的主張。此外，當公司的資本支出偏低時，增加資本支出對公司股票報酬的影響爲負，較偏向自由現金流量假說的認知；然而，當資本支出較高時則較偏向資訊不對稱假說的主張。因此，股票投資人在選擇其投資標的時，應先認知該公司處在支持自由現金流量假說的範圍（即公司資本支出偏低），或是支持資訊不對稱假說的範圍（即公司資本支出偏高），再做其投資決策爲宜。

The purpose of this study explores the relationship between the Free Cash Flow Hypothesis and the Asymmetric Information Hypothesis to investigate whether top managers pursuit their private benefits by using capital investment (hereafter CI) increases, and the effect on abnormal stock returns of firms following increases in CI. We follow the method of Titman et al. (2004), and use Characteric-Based Adjusted Model and Fama-French Three-factor model to test the relationship between CI and stock returns of firms. The empirical results show that if CI increases are positive effects on stock returns of firms, the argument of Asymmetric Information Hypothesis is supported. However, if only considering the sample whose capital investment increases are positive, the advocacy of Free Cash Flow Hypothesis is approved.