The purpose of this study was to analyze the ambiguity of the boundary through the composition of section. The building means the compose of the inside space by physical shell. Inside space that has boundary factors like floor, wall, roof and column is surrounded outside space. The factors which compose the boundary was expressed by architects as various analysis, but it has changed as changing of paradigm and information revolution. The inside space and outside space were connected through the system arrangement, so various space could construct by an aspect of relation. The history of architecture was written as the establishment of in-out space by architectural boundary factors, but the space could not divide definitely, composed complex structure, could experience various recognition. The existing study which is focused on Ambiguity of the Boundary is just focused on contemporary architecture. Ambiguity of the Boundary is developed by using glass. The transparency of glass removed the boundary of space, so it can be created free wall, continuity of view. It was Influenced the boundary of the sight and changed the expression of boundary between the space. This study is to analyze the change of boundary awareness and find the ambiguity of boundary in the section.