不動產先買權涉及不動產的有效利用，向來是實務上重要問題，但相關學說研究仍有不足。例如依土地法第一０四條規定，基地之地上權人或典權人出賣房屋時，基地所有人有先買權；不過，參酌民法第八三八條第三項及第九一七條第二項規定，基地的地上權人或典權人出賣房屋時，應一併出賣其地上權或典權（即權源），而不得僅出賣房屋。此際，基地所有人是否仍有先買權？如有，先買權的客體為何？就此二問題均有不同見解。本文先析究上開規定的規範意旨與適用上應注意之處，作為全文探討的基礎，再探討前開二問題。本文著重於相關當事人的利益衡量分析，並希冀促進不動產的有效利用；本文就既有的學說、實務見解予以回應，並提出解釋論上的建議。本文以為，基地的地上權人或典權人將其房屋連同權源一併出賣時，基地所有人仍有先買權，其行使先買權時應一併購買權源。 The right of first refusal refers to effective utilization of the real estate and is an important issue in practice. However, the existing studies are insufficient. For example, according to Article 104 of the Land Act, the owner of the building site has a right of first refusal when the superficiary or the dian-holder of the site sells his house. However, according to the third paragraph of Article 838 and the second paragraph of Article 917 of the Civil Code, the superficiary or the dian-holder of the building site shall sell the superficies or dian at the same time when he sells his house. He cannot only sell his house. In this situation, does the owner of the site still have the right of first refusal? If so, what is the object of the right of first refusal? There are controversies over the two questions. First of all, this study analyzes the purposes and the issues we shall notice when the above provisions are applied as the foundation of this whole article. This study then explores the said questions. This study emphasizes the interests of the concerned parties and promotes effective utilization of the real estate. This study discusses the existing doctrine and practice and makes some propositions in explanation. This study holds that when the superficiary or the dian-holder of the building site sells his house and his right together, the owner of the site still have the right of first refusal. When he exercises his right of first refusal, he shall buy the superficies or dian together.