This research attempts to investigate the required performance of the buildings. The construction cost is the major factor which represents the level of the required performance. The change of construction cost is assumed to be caused by two factors, the change of the unit cost itself and the change of the required performance. The analytic method of the required performance is finally proposed by the data analysis of the change of construction cost by using these two factors. Also, an example of the analysis of the office building by using this method is shown.