速食食品不但在我們的生活中扮演重要的角色，在台灣，其亦是最重要的餐飲產業之一。文獻上有關於加盟總部與加盟商之間的決策背後的模型，各個因子如何影響彼此，最後加盟總部與加盟商皆能極大化他們的效用，達到一個最適加盟的平衡點。然而，未看到有使用校準分析(Calibration)的方式回推出無法觀察到變數之合理區間的文獻。本研究使用此方法及台灣麥當勞的資料來解開加盟與否決策背後模型的面紗。在最基本的經濟模型中，我們發現加盟商努力的重要性增加時會導致加盟率的下降。再者，都會區的加盟商風險趨避程度以及市場風險較非都會區高。為了針對麥當勞總部的市場策略，延續上個模型的設定，我們在生產函數中另外加入健康食品的產品線以建設出較細緻的第二種模型。此延伸模型相較於第一個模型能解釋更多資料。我們亦觀察到當健康食品佔麥當勞產能提高時，模型的適配度會下降。此現象可解釋為在其他條件不變下，當麥當勞在菜單內加入更多比重的健康食品時，加盟商與加盟主的獲利將低於現階段的水準。 關鍵字: 速食產業，委託代理理論，校準分析，加盟 / Fast food restaurants play an important role in our daily life; they are also one of the most important restaurant business types in Taiwan. The literature posits and examines models behind how franchisors and franchisees reach their franchising decisions, and how different factors affect optimal franchising rates. On that basis, they derive the optimal franchising rates, at which both franchisors and franchisees can maximize their utility. However, there is no literature on determining the reasonable range of variables in the model that we cannot observe in the real world. This study takes the initiative to unveil the model behind the franchising decision with proxies of variables by calibrating a basic economic model using data from McDonald’s Taiwan. Our finding are that a higher importance level of effort results in a higher optimal franchising rate, and the level of franchisees’ risk aversion and the market risk in metropolitan areas are higher than in non-metropolitan areas. In accordance with McDonald’s Taiwan’s strategy in the past years, we construct a more detailed model to capture the characteristics more accurately by adding a healthy food product line into the production function. The extended model can explain the real-world data better than the previous model. On the strategy side, we find that if healthy products account for a higher proportion of the production capacity, the model fitness level drops. In other words, the profit for both the franchisor and franchisees decreases when McDonald’s Taiwan introduces more healthy food to the menu. Key Words: fast-food industry, principal-agent model, calibration, franchising