民法第四二五條規定了讓與 (買賣) 不破租賃，往昔學說多從保護弱者的觀點來加以理解。本文則從保障長期投資的觀點出發，重新詮釋此一規定。本文建立在前人提出的物權效力有減少交易成本之用的理論上，論證了讓與下破租賃在我國過少物權種類的情形下，正有補足此缺憾的功能，因此活絡了租賃市場，但其要有相應的公示制度配合，否則債權替代物權而增加交易成本的情事，會轉移發生在物的買賣市場，將導致貨不能暢其流。基此，本文說明了動產租賃為何下具重要性、法院為何從寬認定不動產上的租賃以及縮小受讓人應負押租金返還責任的範圍、立法採取強制公證是否矯枉過正、以及使用借貸與共有物上的分管契約為何下得類推適用讓與下破租賃等爭議問題。

　　　　　In contrast to the usual property/contract divide, § 425I of the Civil Code provides that the lessee still can claim rights under the lease contract against the buyer of the leased property. Most scholars attribute this exceptional provision to protecting the weaker party, i.e., the lessee. This paper draws upon a point contained in an earlier Supreme Court decision and develops a perspective of protecting long-term investment. Based on the thesis that the absence of in rem rights would increase transaction costs and reduce the volume of transactions, this paper attempts to explain why the lessee needs the in rem rights to protect his long term investment. As the range of in rem rights provided in the Civil Code is severely restricted because of the numerus clausus principle in property law, this provision has the capacity to stop the gap. However, an appropriate notice system should be attached to prevent transaction costs from increasing in fire sale market, otherwise the benefits gained in the lease market would not compensate the loss incurred in the sale market. With this theory in mind, this paper sets out to explain some puzzling court decisions and argues that the principle of "like cases should be treated alike" should not be invoked to deem the contract of loan for use or the contract of sharing among co-owners as equivalents of the contract of lease.