PURPOSE: To improve usability of a room by providing a skip floor along each side of a wall body dividing adjoining spaces and providing a movable base in an opening formed at the lower end of the wall body so as to be movable to any one of the spaces.

CONSTITUTION: A movable base 5 provides a floor 5a of various area and can be used for various purposes in rooms 1, 2 depending on the movement thereof. Next, if the base 5 is moved to any one of the rooms 1, 2, the other room can be used as a large room having no step. And when the rooms are constructed and one of building units is installed, the base 5 is stored in the adjoining other unit and after installing both the units, if the base 5 is moved into an opening 4, the units can be set without being interfered by the base 5. And the base 5 is utilized as a bed, sofa, base of mat, etc., and further can be used as an article storage in both rooms. As a result, each of the rooms and the movable base can be utilized for various services and construction can be easily performed.