本文主要探討主併公司在併購後會產生何種效果。併購動能可以造成市場掀起一股併購的熱潮,但是何種因素會產生併購動能並且造成市場併購盛行呢?結果在本文發現台灣市場上產生併購動能的因素來自於經理人的自利主義。經理人因為害怕市場併購盛行的當下,公司因此而被併購而其職位不保或免職,促使經理人借由做出併購的決策以避免被其他公司所併購。然而,此類型的併購通常會損及公司價值,造成併購宣告的同時,市場的反應也會給予不好的回應,其股價表現低於大盤;長期相對於大盤的超額報酬表現,亦會有相同不好的結果。 This thesis examines the effects of mergers on bidding firms’ stock price. Merger momentum could lead to market has a merger wave. There are different explanations for merger momentum. We find evidence of merger momentum that bidding firms do a merger to prevent managerial private benefit. If there is a merger wave, then the managers are willing to do a bad decision. As a result, merger announcement abnormal returns could be negative correlation to the bidding firms’ past stock performance. In the long run, there is a similar result for bidding firms.