本文以1995年至2019年做為樣本期間，採用台灣上市櫃併購案作為樣本，探討目標公司股權集中度對主併方股東財富之影響，本文以目標公司前三大股東持股率做為股權集中度之衡量方式。
結果顯示，由於目標方股東要求較高的合約價使主併公司付出過高價格，因此股權集中度高之目標方長期會損及主併方之股東財富。目標方股東並未考慮併購為目標公司帶來的價值，而以自身利益為優先考量，顯示股權集中度高之目標方存在代理問題。此外，本文亦於研究過程中發現主併方於併購取得之股票比例短期能增加股東財富，但長期則損及股東財富。推測短期市場對併購樂觀預期，預期取得大量股票後能成功整併帶來綜效；但長期則因取得大量股票所帶來的財務壓力，以及整併上的困難，造成主併方選擇風險較低的營運策略而非專注提升企業價值。
本研究建議主併公司將目標方股權集中度納入併購決策，選擇適合的併購標的並審慎決定取得目標方之股權比例，避免對未來營運造成負擔。

Based on the mergers and acquisition (M&A) deals of Taiwanese listed and the OTC acquiring companies from 1995 to 2019, this thesis investigates the impacts of the target firm’s ownership concentration on the acquiring firms' shareholder wealth. I use the target company's percentage of the top three shareholders' shareholding as the measure of ownership concentration. In addition, I choose cumulative abnormal stock return and buy-and-hold abnormal to evaluate the market reactions to the bid through the event study methodology.
The empirical results indicate that target ownership concentration is negatively associated with long-run post-acquisition returns. On the other hand, the thesis also discovers that the percentage of shares acquired is positively associated with the short-run return and negatively associated with the long-run return.
From a management perspective, this research suggests that the acquiring company takes the target company’s ownership concentration into consideration because high concentration may contribute to overpayment. Ultimately, this would reduce the firm’s value.

中文文獻
朱文儀、李庭閣、莊正民、廖盈琇 (2019)。大股東股權集中度、外部法人持股、 外部董事年資對公司績效之影響－台灣上市公司的實證研究。中山管理評論， 27(3)，551-582。
陳美華、洪世炳 (2005)。公司治理、股權結構與公司績效關係之實證研究。企業管理學報，65，129-153。
邱俊耀、邱臙珍 (2019)。台灣上市櫃公司併購前之公司特徵對併購後績效影響： 以主併公司為例。當代商管論叢，4(1)，12-34。
陳安琳、湯惠雯、許銘峻 (2000)。企業購併對主併公司股東財富的影響。亞太管理評論，5(2)，171-182。
呂佳玲、林基煌 (2008)。家族企業公司治理、併購策略與績效之探討。亞太經濟管理評論，11(2)，107-134。

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