隨著我國邁入高齡社會，遺囑的數量逐漸增多。遺囑的目的除了財產之分 配外，更重要的是死者遺願的實現，故探究遺囑的真實性極為重要。而判斷遺 囑人之意思表示是否為真，遺囑「要式性」之審查往往是法院判斷工具之一， 而近年來本較不受矚目的「遺囑能力」概念，也逐漸成為法院審酌的重點。我 國繼承法向來以民法第1186 條作為遺囑能力規定，然而，現行實務仍有許多 問題無法僅以該條文作解釋，舉例言之：失智患者、精神疾病患者在患病期間 所為之遺囑等，諸如此類之情況，遺囑人是否具備遺囑能力，將難以依第1186 條處理。本文以我國近十年有關遺囑能力之裁判為主軸，探究實務運作上，對 「遺囑能力」之解釋為何，以及如何解決上開問題，並參考美國法對遺囑能力 之規定作比較與研究。研究發現，實務裁判多以「意思能力」為核心概念，形 塑出一套遺囑能力的判斷標準，故本文將分析遺囑能力在學說及實務上之解 釋，以及第1186 條之運用現況，最後整理及歸納我國實務之判斷方法，進而 提出本文結論。

Whilst Taiwan steps into an aged society, the numbers of testaments increase accordingly. Apart from the purpose of distributing the property, more importantly, a testament implements the will of the testator; hence, it is vital to probe the authenticity of the testament. To investigate the formality of wills is usually one of the methods for the court to judge if a testament is authentic. In addition, the concept of mental capacity did not receive enough attention until recent years; it has gradually become an important discretion of the courts. In Taiwan, the inheritance law usually defines the testamentary capacity by Article 1186 of the Civil Code; however, there are some issues that the Article was insufficient for explaining it. For example, a testament made by the patient with dementia or mental illness during the outbreak, it would be difficult to define if the testator had the testamentary capacity purely based on Article 1186 of the Civil Code. This research collects the judgment regarding testamentary capacity in Taiwan in the past decade to conclude the actual definition of the testamentary capacity in realistic practice and explain the solution of the above issues. Further to take the definition of judging the testamentary capacity in the Common Law in the United States as a reference to compare with the research. From the study, most of the implementation of the judgment takes the mental capacity as the core concept to shape the standard of judging the testamentary capacity. As a result, this research analyzes the definition of testamentary capacity theoretically and practically, discusses the current condition of the Article 1186, organizes and summarizes the judging standard of the implementation in Taiwan, and therefore generate the conclusion of this study.