This paper deals with Adolf Loos's urban planning for Vienna where he was active as an architect and a critic. The purpose of this paper is to show the following. First, to clarify construction-principles and the ambiguous character of his urban planning. Secondly, to point out critical contents of his urban planning and make clear a structure of its critique. His urban planning's ambiguous character originates in quarrels between parts and the whole of his plan. Then his utopian urban planning's critical power arises from a sharp difference between reality and possibility of modern Vienna.
