共有土地除因其使用目的不能分割或契約訂有不能分割之期限外，為促進共有物之利用，使共有之關係消滅，於公私皆有裨益，故民法第八百二十三條乃明定，各共有人得隨時請求分割共有物。惟原共有人以其應有部份設定抵押之抵押權，究應存在分割後該共有人分得之部份？抑或仍存留於原共有物分割形成之全體單獨所有之上？依現行民法第八百六十八條規定意旨抵押權具有不可分性，故抵押之不動產如經分割，其抵押權不因此受影響。惟此規範是否及於應有部份設定抵押權，恐有爭議。就抵押權人立場而言，為獲得充足之擔保，當主張土地分割後其抵押權仍存於分割後之每一宗土地。就共有人而言，為確保其產權之圓滿，當主張土地分割後抵押權應存在於抵押人取得之土地。現行土地登記規則與民法物權編修正草案，亦呈不同之規範。這些規定與見解各有所本，本文擬由法律經濟觀點，進行研析，期能提供不同思考途徑，以供參酌。

In order to improve the utilization of common property, the Civil Code, Article 823 provides that “each co-owner of a common property may request for a subdivision of property rights”. But before subdivided the said land with multiple ownership, each co-owner is free to create a mortgage on their entitled share of land ownership. If some of the co-owners create a mortgage on their entitled shard of land ownership when the land is undergoing a subdivision, shall the mortgage be transferred to each subdivided land according to the original entitled share or only be transferred to the land to which the original creator is entitled after the subdivision? We found that mortgagee and other co-owners shall be equally concerned with this issue, which implied that the subdivision registration (Article 107 of The Land Registration Regulations) shall be revised.