To reduce a confirming work facility by comparing a facility not inputting a constant by a system to be calculated with a constant of an adjacent facility before an analytical calculation, and displaying a list of remarkably different constants and unconnected facility.

A confirming function conducts an analytical calculation 2 based on a drafted power system diagram 1, and selects possibility or not A1 of execution of a facility confirming function in a system to be analytically calculated before the calculation. If the system does not have an incorrect cause in the facility constant, a calculation execution 3 is executed, and a calculation result display 4 is then conducted. If a facility constant of the incorrect cause is discovered in the possibility A1 of the facility confirming function, a list A2 of the incorrect cause facility is displayed, and a calculation execution A3 is conducted by the facility constant. If no incorrect cause exists, the display 4 is similarly conducted. Thus, even when a result after the calculation and a calculation result by a human system are conducted, cause factor can be displayed at a list without individually searching the causes, and an operator's constant confirming work can be largely alleviated.