To plot via on a display screen so that layers that are connected by via may intuitively and easily be decided in a printed circuit board pattern design processor.

A processing part 2 reads position data of via on a layer, layers connecting data and prescribed shape data from a storing part 3. The prescribed shape is divided into layer sections D1 to D6 which correspond to each layer and shown at a position of a display part 4 which corresponds to the position data, and also, via section V that corresponds to layers which are connected by via based on the layers connecting data, synthesized and shown. Furthermore, plural sections V that exist at the same display position are combined and shown.