本研究之主要目的在於探討公司自由現金流量與其過度投資之關聯性，並設法瞭解內外部機制是否有助於減緩公司過度投資之代理問題。此外，本研究亦探究公司自由現金流量與債務控制之關聯性，以及債務控制與公司之其他監督機制間之關聯性。本研究發現，公司自由現金流量愈大時，愈可能有過度投資之現象，且此種現象較集中於自由現金流量為正之公司。此外，相較於高成長公司，低成長公司自由現金流量之代理問題較為嚴重，更傾向於過度投資。而在減緩代理問題之機制上，管理階層及機構投資人之持股並無法有效減緩代理成本，或抑制公司過度投資之現象，但或許可藉由債務控制減緩過度投資之問題。再者，本研究推論過度投資之公司可能會傾向於提前適用資產減損之會計處理，以認列其投資損失。最後，公司代理問題愈嚴重時，並不一定會藉由債務控制方式減緩過度投資。而在降低代理成本的作用上，管理者持股、機構投資人持股與債務控制之間具有明顯的互補關係。 / The main purpose of this study is to examine the association between a firm’s free cash flows and its overinvestment. In addition, I also examine the interrelationships between free cash flow, managerial ownership, institutional investors, and debt .The empirical results suggest that overinvestment is concentrated in firms with higher levels of free cash flows and lower opportunities for growth. Further tests find that a firm’s managerial ownership, institutional investors’ ownership may not effectively mitigate its overinvestment. However, debt appears to control overinvestment. Besides, I infer that firms with overinvestment may choose to adopt the accounting standards for asset impairment earlier to recognize their investment losses. Finally, I find evidence that firms may not be using debt control to mitigate their overinvestment, and a firm’s managerial ownership, institutional investors’ ownership and debt may serve as substitutes in controlling its agency costs.