From long time ago, stairs are performed the central role of vertical circulation system in architectural planning for convenience of human. The purpose of this study is to find the spacial characteristics of stairs in architectural space. Two methods In this study are discussed. First, it is to extract the formal elements in its stairs shape raising an impulse of visual-perceptible recognition. Second, it is to analysis its characteristic through relationship between stairs and spacial elements. In conclusion, the characteristics of stairs in architectural space have as follows 1) spatial connection - to connect between space and other space or masses; 2) spatial separation - to separate between inner space and other space; 3) openness or closeness of space; 4) directed-tention of space.