在進行捐贈行為時，若以極大化個人效用為出發點，捐贈者首要應以慈善組織的理念與關懷對象與自身關懷對象是否相近為主要考量，本文將此關懷對象的定位定義為慈善組織的區位，討論慈善組織在競爭上的區位策略。除此之外，同時也將慈善組織的規模與公信力對捐贈者的影響力納入考量。 本文以線性城市（linear city）模型補捉捐贈者與慈善組織的關懷對象的區位，並考慮到捐贈者對於慈善組織規模的考量，將傳統應用在電信產品的「網路效果」引入捐贈者的效用函數中，同時考慮區位差距與組織規模對捐贈者的影響。本文研究後有幾點發現：第一，慈善組織為了避免過度的募款競爭，會避免服務對象的性質過度重疊；第二：網路效果的引入會加劇慈善組織之間的競爭進而提升慈善組織的募款努力程度；第三：當慈善組織之間的網路效果規模有差距時，捐贈資源會集中到規模較大的慈善組織，同時規模較大的慈善組織會擴大其服務對象的範圍，而規模較小的慈善組織所得的捐贈資源也會因此減少。 / Naturally, utility maximizing donors first consider charities sharing their same ideology towards those in need of helps. Therefore, in setting up fund-raising charities, the choice of “location”, in the spectrum of all potential donees, will have effects on the fund-raising results. In addition, donors also often take into account operation scales and credibility when it comes to choosing among different charities. This study proposes a model that the location choice of two homogenous charities is captured through a linear city framework, and a “network effect” in the utility of donors is introduced to account for the influence of scale and credibility of charities. Several findings emerge. First, in equilibrium, charities differentiate in the choice of location to avoid intense competition in fund-raising efforts. Second, the existence of network effect drives competing charities to exert more fund-raising efforts. Third, asymmetric network externality has the effect to redistribute donations away from the small network charity when the large network charity moves towards to “center” of the market. Finally, some welfare implications are explored.