PURPOSE: To improve the utilization efficiency by continuously installing a staircase as blind which partially partitions the contiguous room spaces at the boundary and the accommodation furniture.

CONSTITUTION: At the boundary between a living room space 2 and a dining room space 3, a staircase 10 which serves as a blind for partially partitioning both the spaces and the accommodation furniture 20 are installed continuously. The staircase 10 is constituted of a straight advance staircase, and the part below is formed to a concealed state so as not to be viewed through both the spaces 2 and 3. For example, at the side surface part of the dining room space 3 side, a both-side opened type accommodation part or an opening/closing door type accommodation part is formed, and one end side of the accommodation furniture 20 is formed continuously to the back of the staircase 10, and the other end side is formed to an integral state or the contact state with the wall body 60 part between the entrance/exit 2a of the living room space 2 and the entrance/exit 3a of the living room space 3. The accommodation furniture 20 has a height ranging from the floor part on the first floor to the ceiling part, and the necessity of separately installing the wall body and a screen for concealment is obviated by installing the accommodation parts 21 and 21 which are opened and closed by the both-side opened door, etc., which are installed on the left and right surfaces.