PURPOSE: To quickly provide a building plan and a building drawing by sectioning the flat face of a selection plate into plural areas in accordance with the azimuth of a building and displaying the building plan of desirable type in each area.

CONSTITUTION: The areas are made into patterns with the position of an entrance and water utilities as a center and respective types become eight kinds of plans 1 to 8 by giving a rotary operation and an invertion operation. Then, as a precondition, restrictions by the Building Standards Law., namely, the building coverage ratio, the floor area ratio, an oblique line, a site, the position of a road and an azimuth are confirmed. At the same time, a building possible area by the restrictions of a parking lot, lighting and the oblique line is examined and the position of the entrance applied from the relation between the site and the position of the road is seleced by regarding the selection plate as the building. Furthermore, an optimum plan is selected from a building plan selected in accordance with the azimuth of the building and a plan selected in accordance with the shape of the building, a size or a volume is decided together with at this time.