「傳媒外部性」是指傳媒在生產其內容、或閱聽人於消費該內容的過程中，對於非關該市場交易之第三人產生影響，致使傳媒活動可能侵害第三人的權益，抑或可能創生公共利益的現象。作為一種傳播效果，以及一種構成市場失靈、從而需要公共政策介入的概念工具，「傳媒外部性」可以作為聯繫「傳播效果」與「媒介政策」的研究橋樑，因此對於拓展跨學科的溝通，具有潛在貢獻。 外部性是衍生自主流經濟學的概念，其測量無法不涉及量化指標（如貨幣），惟本研究亦闡明：該概念之內涵不可能、亦不應該完全以量化標準來看待；就此檢討後，本研究參照公法學教授Edwin Baker所提之十種傳媒外部性類目，同時酌量採納傳播效果研究的部分成果，提出本研究分析傳媒外部性的類目指標，並試圖使經濟學與傳播研究在對話中，能豐富各自的內涵。 透過相關文獻的檢視與分類，並針對《壹週刊》內容所創生的外部性予以歸納分析，本研究將歷來對於傳媒外部性的回應方式，分做三類八種。第一類是指行政立法部門的「傳播政策」回應，又可略分為宏觀結構管制（傳播哲學、產權與財源的確立）、微觀結構管制（庇古稅及津貼）、經由政府授權以形成三方對傳媒的共管，以及對傳媒內容的規範等；第二類則為民事與刑事等對於特定傳媒內容之「司法仲裁」回應；第三類回應則涉及「市場規則」，又可略分為媒體素養課程之推廣、媒體監督組織的運作、及傳媒與外部性承受者間的私下協商等。由於傳播政策可以是統合或中介前述三類回應的關鍵，本研究最後就公共政策介入以創生優質傳媒環境的作用，提出初步的反省。 / During the production and consumption process of media content, a certain ‘media externality’ is inevitably created that may benefit or harm the third parties who actually are not present in the market exchange relationship between the producers and their audience. Therefore it’s reasonable to conceive ‘media externality’ as one aspect of communication effects, and as a factor that contributes to market failure, as such, this thesis suggests that we employ ‘media externality’ as a conceptual tool bridging ‘communication research’ and ‘media-policy research’ in a way that both disciplines can contribute to each other. To measure ‘externality’, it’s not possible that quantitative indicators such as ‘money’ be not invoked, meanwhile it’s neither desirable nor feasible if economic calculation or consideration exhausts what we mean by ‘media externality’. Having established this methodological principle, and in addition to bringing in relevant communication effect researches, the author builds and expands upon Edwin Baker’s categorization and proposes my own framework for measuring ‘media externality’. It is hoped that communication science and economics can enrich respective tradition via this dialogue. The ‘Next Weekly’ is then subject to a careful investigation and its externality is subsequently assessed. In all, to deal with media externalities, three models with eight variants can be discerned. To begin with, there is a ‘policy dimension’ comprising macro-structural regulation that attends to communication philosophy, arrangements of media property rights and finances of media production. The second policy element is of a micro-structural regulation nature, including Pigouvian tax or subsidy. Also, the state may stipulate that its regulatory power be shared with the industry and the audience’ alike. The second model indicates civilian or criminal lawsuits. Lastly there is a market response to media externality, be it the promotion of media literacy, operations of media watch groups or individual victim’s compromise with the media. This thesis ends in a reflection, since by its definition communication policy is bound to step in all the other variants, that evaluates the relationship between public policy and a more healthy media ecology.