This building is built on the flatland in the central of Oita City. This is a project reconstructed due to the expansion of office,with mixed surroundings of residence,commercial facility and schools. The office before reconstructed was built on a rectangular site, with all the affairs dealt with in such a 40-tsubo wooden one floor house. For the site, only the east side faces the road of big traffic. Based on the expansion of the office, the architects will guarantee in their plan the maximum parking vehicles. As a result, starting from the parking plan, the pilotis will be naturally used. Furthermore, two 2-story boxes with different sizes shall be prepared on this pilotis. As required, the office should have open-type arrangement to keep the 15-20 staffs working in an environment easy to control and communicate. In addition, the entire building is made up of reception room, discussion room, and senior management room. On the west side set up the office and the marched storage room and discussion room; while on the east with rooms which can be opened to a certain degree in respect to the roads. Furthermore, the east and west side are connected with a gallery so that the exterior vision of office can be blocked out, ensuring a minimum daylighting. The box on the west side is larger than that on the east, which allows the acquiring the exterior scene from the interior and gives changes to the lines with barren outlook. The facade emphasizes the design of quadra shaping the box type. Additionally, steel structure as it uses, this building adopts the exterior-attached thermal-insulated ventilation construction process to the wooden furring strips, and also considers the temperature environment indoors.