追溯近代世界各國監察制度的濫觴，因為時代與文化背景以及政治體制的不同， 所以成立的原因各異。為了釐清監察制度存續的必要性，實有必要先探究其發展之 淵源。故本文先以歷史制度的角度分析監察制度的發展，並植基於理性選擇當中效 益最大化的觀點，將我國監察院從2008 年8 月至2014 年7 月為止，因為行使法定 職權所花費的成本與獲致的財務效益予以貨幣化，並從事成本利益分析。除此之外， 本文也以演繹的途徑，從利害關係人的心理取向分析監察制度當中最重要的功能─ 「受理人民陳情」的救濟成本。 以理性選擇途徑衡量政策或制度的取捨雖然有其限制，尤其對於重視公共性的 政府機關更是如此，因為理性選擇觀點無法涵蓋政府所追求的公共性價值。但是， 理性選擇途徑的應用自有其一定的歷史定位與貢獻。因此，本文以理性選擇的觀點， 透過成本利益分析以及利害關係人對於人民陳情成本的心理分析，嘗試論證我國監 察制度存續的理由。

After discussing the historical and institutional developments of ombudsman system around the world, this paper analyzes the performance of Control Yuan (representing the ombudsman system) in Taiwan from the perspective of rational choice. Specifically, the author estimates the monetary benefits accrued due to the investigation and corrective measures exerted by the Control Yuan from August 2008 to July 2014. Meanwhile, the costs are estimated in terms of outlay of the Control Yuan during that time period. Cost-Benefit-Analysis is then employed and the results show that benefits exceed costs, in the sense that the Control Yuan achieves desirable performance and seems legitimate to survive. In addition to conducting the Cost-Benefit-Analysis, this paper also infers, by the deductive way, that citizens would like to file petition to the Control Yuan rather than to apply other possible remedies, because the filing cost of petition is the lowest. Citizens are rational so that they choose the cheaper one. Together with the estimated results of Cost-Benefit-Analysis, the author concludes that the ombudsman system or the Control Yuan in Taiwan is legitimate to exist.