本研究探討過度自信經理人於經濟衰退階段時之併購行為。本研究蒐集S&P1500大企業於1993年至2016年的資料，對過度自信經理人於景氣衰退階段的併購機率、宣告效果、長期股價表現進行分析。因為過度自信經理人低估景氣衰退所造成的高度不確定性，同時高估本身能夠透過併購所創造的公司價值，我們預期過度自信經理人相較非過度自信經理人更容易在景氣衰退的階段進行併購。然而實證結果過顯示過度自信經理人的併購機率於2008年金融海嘯後大幅下降，減少併購的幅度顯著高於非過度自信經理人。此結果和過去文獻一致，說明在財務資源不足的情況下，過度自信經理人會比非過度自信經理人更不願意投資。因為過度自信經理人高估自家公司權益價值，認為資本市場低估其權益價值，就算面對能為公司創造價值的投資案時也不願意向外發行股票籌資，因而導致他們在經氣衰退時較非過度自信經理人投資更保守。 / The study examines the behaviors of overconfident CEOs during recessions using firms included in S&P 1500 Index from 1993 to 2016. We propose that overconfident CEOs would undertake more M&As than non-overconfident CEOs during recessions for their biased beliefs lead them to underestimating the risk they would incur in recessions and overestimating the synergy they can create through M&As. However, we found that, during and after the 2008 Recessions, overconfident CEOs reduce significantly more in undertaking M&As than non-overconfident CEOs. The results are consistent with past literatures and suggest that decrease in financial resources caused by recession lead overconfident CEOs, who overestimate the value of their own equity and are unwilling to issue new equity, to reducing more in undertaking M&As than non-overconfident CEOs after and during recession.