This study aims to understand the ornamental space in Art-Nouveau style which was made up the ornamental aspect and spatial aspect. So that It is needed to classify the ornamental space into three categories according to the way of construction; pictorial composition, non-objective composition and organic construction. To find the meaning of these ornamental spaces, works of Art-Nouveau are analyzed into ornament and space, in result we know that process of integration, relativity of ornament as a part and forms of expression in ornamental space have some regulation; use of natural motive, repetition of image and organic combination. Whereas the ornamental space in Art-Nouveau style has comprehensive capacity between antagonistic relations just like tradition and new mechanism, the space could receive a lot of different ideas and express these ideas as ornaments. Although the ornamental space also had weak points which were the lack of transformation and the difficulties of the application of other design due to the perfection itself, we could create new space which meets the requirements of the times, if we develop and make up for the weak points in the ornamental space under the principles of dialectic.