在現今的國際社會中，多邊主義儼然已經成為大多數國際建制的運作模式。然而我們必須瞭解的是，多邊主義作為一種國家間關係運作的模式，它所代表的意義不只是許多國家聚集在一起，更蘊含著參與國必須遵行共同的遊戲規則、並且各自有著自視為成員的向心力等重要的意涵。因為其運作存在著這些特性，全球性的多邊主義機制大大裨益國際秩序的建立。儘管這個重要的概念直至九O年代才被真正突顯出來，但從過去國際關係的發展經驗來看，多邊主義早已運作良久，而其強調的概念也可詳見於各種國際關係理論之中，因此，此概念的提出，重要性可見一斑。 本研究先從歷史脈絡找出多邊主義的相關概念，再以魯傑的多邊主義概念出發，做一理論性的概念分析。而為進一步瞭解多邊主義機制及其內含概念的成形，本研究以歐盟的共同外交暨安全政策作為實例，從其演進的過程中循線找出多邊主義各個概念的蹤跡。從一開始的歐洲政治合作演變成共同外交暨安全政策，歐盟試圖建構出高階政治領域中歐盟國家所應遵行之普遍行為準則，其後又因為共同安全暨防禦政策以及《歐洲安全戰略》的出現，使得歐盟國家逐漸體認到歐盟在國際社會上所應該扮演的角色，因而找出自己的認同，進而強化機制的向心力量。顯然，歐盟的共同外交暨安全政策正在朝著成為一個多邊主義機制的方向邁進，如此進化的動態過程可進一步幫助我們理解多邊主義機制的形成與演化，進而使我們更加瞭解多邊主義的概念。 / Multilateralism is a kind of institutional form and now exists in most international institutions. However, for this term “multilateralism” not only the gathering of many states, but also the common rules all the participants need to follow and the centripetal force from the member states who think they are bound together have to be understood. With these characteristics multilateral institutions are really contributive to the forming of international rules. Though this important concept was not much discussed until the 1990s, we could see it from the working of many international regimes for a long term. Besides, the concepts it stresses were also scattered in all sorts of international theories. Therefore, it must be understood that multilateralism is now one of the most important constitutional concepts for international regimes and from this point of view there should be more understanding in its meaning and its internal workings. The main theoretical discussion of this research starts with John Ruggie’s perspective and some more exploration was made from this viewpoint. To know more deeply the formation of multilateralism and its interior concepts, EU’s Common Foreign and Security Policy (CFSP) was taken as an example to see the evolutional process of a multilateral institution and to find how those above-mentioned concepts emerge in such an institution. From the European Political Cooperation (EPC) to CFSP, European states tried to build up some common rules for high politics. The European Security and Defense Policy and the European Security Strategy then helped them to realize the role European Union should play in the world, to find their identity, to strengthen the centripetal force of this institution. Apparently, this institution is tending to become a multilateral institution. This active development aids the understanding of the formation and evolution of a multilateral institution and the concepts of multilateralism as well.