本文介紹日本「既存不適格建築物」之定義、在建築管理與環境管理上的問題，以及進行管制時對權利人法律上權益之衝擊與法制上的解釋。另一方面，檢視台灣建築法、區域計畫法及都市計畫法相關規定後，發現我國並無「既存不適格建築物」之用語，而有對「原有合法建築物」管制之規定，進一步檢討法規之結構與內容以後，本文認為類如日本「既存不適格建築物」建築管理或環境風險之問題，在台灣亦有存在之可能。因此，日本對「既存不適格建築物」在管理上之因應，以及法制上的解釋，對於台灣亦有參考的價值，並應修正現行法制中有疑義之處，以健全相關法制，落實建築安全和環境管理的目的，保障建築物權利人或其鄰人之居住和財產權益。

The definition of ＂existing non-conforming buildings＂ as described in Japan is introduced in the article. Some other issues, such as architectural and environmental regulations or the protection of residents' rights through legal mechanisms are also discussed in the article. ＂Existing non-conforming buildings＂ is not the vocabulary in Taiwan. Overviewing the articles of the Building Act, Regional Planning Act, and Urban Planning Act in Taiwan, there are some regulations about ＂existing legal buildings＂. Reading through the framework of these regulations and the contents, one could say that Taiwan may have problems similar to those of Japan's ＂existing non-conforming buildings＂. To decrease the risk of disasters which might be caused by unfit buildings and protect residents living in unfit buildings or their neighborhood, Taiwan may have to amend the improper clauses of the regulations and adopt those policies, legislation and interpretations of regulations which have been implemented by Japan.