隨著國內外相關弊案的爆發，「公司治理」近幾年來一直是企業相當重視的議題。除了由於受到國際環境變化劇烈所影響之外，公司治理也與整體企業監控制度有密切之關聯。在國內外有相當多的學者從不同角度進行公司治理的相關的研究，而主管機關如金管會、證交所等也陸續制定相關的措施，希望能夠盡最大的力量來保障投資人的權益。 本研究主要是藉由公司治理的主要變數來探討企業購併案所造成的超額報酬與公司治理之間的影響，並進一步討論當公司治理愈差時，宣告購併所產生的超額報酬是否會較低。研究期間為民國87年1月至97年3月間，曾發生併購活動的上市、櫃公司，共選取100個樣本。而實證結果如下： 一. 經理人持股比例和公司宣告購併所造成的超額報酬呈顯著正相關 二. 大股東股比例和公司宣告購併所造成的超額報酬呈顯著正相關 三. 獨立董事占董事會的比例和公司宣告購併所造成的超額報酬呈顯著負相關 四. 董事會的規模和公司宣告購併所造成的超額報酬呈顯著負相關 五. 市值規模和公司宣告購併所造成的超額報酬呈現正相關，但不顯著 另外，本研究也針對公司治理較差的公司去進行研究分析，發現若公司治理較差的公司去從事購併案時，可賺取的超額報酬愈少，而當公司治理愈差時，這種關係將愈顯著。最後，本研究也彙整一些相關建議，以供後續學者、企業以及政府機關做參考。 / As scandals related to managers and the wealth of investors spring up worldwide, corporate governance has become an important issue recently. In addition to drastic international macroeconomics changes, corporate governance is also strongly influenced by overall monitor systems. Scholars around the world have done lots of research regarding corporate governance for decades. In addition, relevant efforts and measures, aimed at protecting investors’ rights and interests, have also been done by authorities such as FSC and TSE. The purpose of the study is to study the relationship between abnormal return of M&A and corporate governance by examining the factors we choose. Furthermore, we discuss if a company performs poorly on its corporate governance system, whether the abnormal return caused by merger deals will also decrease? 100 samples were selected from the listed companies from TSE and OTC between 1998~2008. Main findings include the following： (1). The ratio of the stock held by managers has a positive relationship with abnormal return of M&A. (2). The ratio of the stock held by major stockholders has a positive relationship with abnormal return of M&A. (3). The ratio of the outside independent directors has a negative relationship with abnormal return of M&A. (4). The scale of the board has a negative relationship with abnormal return of M&A. (5). The market value has a positive relationship with abnormal return of M&A Moreover, the study has also done some empirical research on companies whose corporate governance pale in comparison with others and found that those who do poorly on corporate governance tend to make less abnormal return when making acquisition announcements. Last but not least, the study has also made some suggestions for scholars, businesses and government and hope that they may come in handy in the future.