To enable immediate and easy-to-understand confirmation of heat-dissipation capability only by entering shape data of a radiator without switching screens. Shape data input sections and a shape display section for a radiator, and a graph display section which displays the calculated result as a graph are adapted to be displayed on the identical screen of the screen device. The pattern diagram of a radiator shape and the result of heat-dissipation capability can be seen on the graph simultaneously only by entering the shape data of the radiator without switching the screen.