隨著企業經營規模日趨複雜、專業化，股東因人數眾多、股東意見不一，在面臨公司所有與經營分離所產生的代理成本控制上，實有困難。一般小股東因持股過低，對於公司經營事務只能消極以待，若對公司經營成果不滿意，只能選擇華爾街準則(Wall Street Walk or Vote with Feet)，而賣掉股票，甚難對管理階層進行更進一步的影響。相較之下，機構投資人基於其人力及資源優勢，能深入參與公司治理、監督管理階層，進而提昇公司經營績效，增進股東投資價值，此即為機構投資人積極主義。 本篇論文探討機構投資人行使股東權以促進公司治理發展。首先討論機構投資人積極主義之兩大基礎支柱－其一，良好公司治理確能對公司績效表現有所助益，其二機構投資人促進公司治理乃其善盡受託義務之體現。 由於美國機構投資人主義高度成熟發展，而國內機構投資人積極主義仍屬起步階段，本篇論文即以比較研究法，探討美國機構投資人行使股東權如股東提案、委託書投票、直接與管理階層溝通、發布黑名單、團體訴訟與股東提名董事草案等，及分析說明我國公司治理相關條文與機構投資人行使表決權時所會遭逢之困境。 此外，本論文經由案例研究，深入蒐集資料並訪談兩個在促進公司治理領域夙負盛名的退休基金-美國威斯康辛州投資委員會與加拿大安大略省教師退休計畫，從而細膩地觀察美國及加拿大機構投資人積極主義之發展、瓶頸與挑戰。 最後，本論文提出促進機構投資人提出公司治理及表決權行使政策、鼓勵機構投資人於股東提案權與表決權等議案進行合作及建置對機構投資人餐與公司治理友善之法規環境等建議，期能對於我國機構投資人積極主義之發展有所助益。 / The increase in institutional funds has been extraordinarily rapid. Comparing with the minority shareholders, the institutional shareholders’ size and expertise can minimize the collective choice problem and agency costs. Their resources enable them to investigate and monitor management in corporate governance field. This is the “Institutional Shareholder Activism“. This article discusses the institutional shareholder’s enhancement of corporate governance. It explores from the two backbones of the Institutional Shareholder Activism: Firstly, the correlation between corporate governance and corporate performance, and secondly, fiduciary duties of the Institutional Shareholder. It makes two conclusions: Good corporate governance certainly helps protect shareholder interests, and contributes to superior long-term economic performance, and institutional shareholders can comply with fiduciary duties by enhancing corporate governance. Furthermore, due to America institutional shareholder activism is highly developed, while Taiwan institutional shareholder activism is not developed. This paper compares America institutional shareholder activism with Taiwan’s. It discusses America institutional shareholder activism in many aspects, such as shareholder proposal, proxy solicitation, vote, direct negotiation with the corporate management, focus list, class action, security holder director nominations bill etc. Then, it analyses some of Taiwan’s corporate governance related articles such as shareholder proposal and security holder director nominations, and some difficulties which the pension fund and the security investment trust fund face when they vote as shareholders. Moreover, through case study, this paper analyses two prestigious pension funds: State of Wisconsin Investment Board (SWIB) and The Ontario Teachers’ Pension Plan (OTPP), and investigates their stages of development and current operation and future challenges in the corporate governance field. At last, this paper provides some suggestions and inspirits the institutional shareholder activism in our country.