近年來出現之大型及超大跨國線上數位平臺已成爲數位經濟之重要結構，除作爲終端與企業用戶間之資料中介者外，還會提供數位服務與產品，並從產業之網路效應中獲利，而其中有能力提供核心平臺服務者，也同時具有限制其他業者進入產業市場之控制性地位，故被視爲數位「守門人」（Gatekeeper）。歐盟《數位市場法》之立法目的，即爲預先強化歐盟境內的市場監理機制，有效降低線上中介服務供應商、捜尋引擎及社群媒體等數位守門人對用戶自主性之限制，保障市場競爭性與公平性，並提升公民參與及協同合作治理平臺之可能性。這些守門人控制數位市場，並以自訂管理規則控制用戶行爲，造成用戶對平臺之高度依賴，同時亦形成守門人與部分企業在市場競爭上之限制競爭行爲，阻礙市場正面發展。若無歐盟層級之法律規範，則守門人對市場控制地位與權力之濫用，將導致歐盟共同市場的崩解。對此，本文分析歐盟如何透過《數位市場法》事前預防守門人減弱市場競爭性、剝奪個人與企業用戶自主性，干預數位市場自由運作及損害歐洲消費者權益等行爲，並以數位平臺之規範性權力爲理論途徑，探討數位守門人如何形成市場權力，以及《數位市場法》立法後，如何監理守門人權力濫用行爲與該法可能之規管效果。

The large-scale international online digital platforms that have emerged in recent years have permeated the public sphere, with the majority of them benefiting from the network effects of specific industries that have been integrating them into their own ecosystems. These platforms have become an integral part of the digital economy as they facilitate a large number of transactions between end users and businesses. However, they also extensively track, profile, and archive end users. Some platform operators have added multiple functions to serve as digital “gatekeepers” between end users and businesses. The operators of such platforms typically occupy a recognized and fixed position. This position is based on the accumulated operations surrounding the core platform service system. As a result, platform operators have created barriers and restrictions that hinder new operators from attempting to enter the market of a particular industry. The goal of the EU’s “Digital Markets Act” is to strengthen the EU’s market supervision mechanism prior to any further expansion of the market dominance of various digital platforms. This effectively reduces the restrictions on investor autonomy imposed by online intermediary service providers, search engines, software stores, and other digital service providers. It also increases the likelihood of citizen participation and collaboration on platform governance while ensuring market competitiveness and fairness. These digital gatekeepers have extensive control over the digital market and regulate user behavior through platform-defined norms, causing users to become overly reliant on the platforms. Furthermore, they foster restrictive market competition between gatekeepers and specific companies, impeding the market’s potential for positive growth. The gatekeeper’s control of the market and abuse of power would result in the disintegration of the EU’s common market in the absence of legal regulations at the EU level. To that end, this article examines how the EU uses the “Digital Markets Act” to proactively regulate gatekeepers and prevent them from undermining market competitiveness, depriving personal and business users of their autonomy, interfering with the free operation of the digital market, and violating the rights and interests of European consumers. The normative power of digital platforms provides a theoretical framework for investigating how digital gatekeepers gain market power, how to supervise gatekeepers’ abuses of power, and the potential regulatory effects of the “Digital Markets Act.”