本文利用BDE的CUSUM-SQ/sub s/方法檢定股價的結構變化時點,再應用事件研究法來分析台灣企業從事海內外購併之宣告對股東財富的影響。實證結果發現全部購併事件對台灣主併公司的股東財富有顯著的正面影響,其當日異常報酬為1.82%,而整個宣告窗口[-5,5]則為不顯著的正異常報酬1.18%。將全部購併事件分類,我們進一步發現國際購併確比國內購併對主併公司的股東為佳,即正國際網路效果顯然存在。又水平相關購併較非水平相關購併能帶給主併公司股東大額異常報酬,即水平相關效果存在。而且高科技產業購併較低科技產業購併對主併公司股東有利,即產業科技效果有作用。但採用現金方式購併較採換股方式購併對主併公司股東不利,違背Myers & Majluf (1984)的資訊不對稱假說,此有待進一步實證研究分析。 This paper uses Brown, Durbin and Evans' (1975) CUSUM-SQ/sub s/ method to search for the switching points of structural change, and then examines Taiwan's acquiring firms' shareholder-wealth-effect by means of event-study methodology. The empirical results show that there is 1.82% significant average abnormal return on event day 0 for the shareholders of Taiwan's acquiring firms, while their cumulative average abnormal return is insignificant 1.18%. Furthermore we find that international M&As perform better than domestic M&As for acquiring firms' shareholders. This implies that the positive international network effect does exist. In addition, horizontal M&As bring higher abnormal returns to the acquirers' shareholders than non-horizontal M&As. It shows that the horizontal relatedness effect is crucial. And the hi-tech industry M&As create more wealth to the acquirers' shareholders than low-end industry M&As. This result shows that the industrial technology effect makes outcomes different. Finally and most importantly, we find that cash-exchanged M&As performs worse than stock-exchanged M&As. The medium of exchange effect does exist in Taiwanese case but it is contrary to the theory and evidence of Myers & Majluf's (1984) information asymmetry in American cases. The last result should be investigated further.