PURPOSE: To execute the printed circuit board design with high accuracy by calculating three-dimensional wiring length which considers plate thickness of a printed circuit board, based on printed circuit board design data, and checking a wiring length limit of the printed circuit board by this calculated wiring length.

CONSTITUTION: A DRC part 22 calculates planar length (planar wiring length) of a wiring pattern, based on inputted design data of a printed circuit board 30. Subsequently, the DRC part 22 derived length (height) of a via 33 for connecting both patterns between wiring layers from thickness of several wiring layers concerned, adds it to planar wiring length derived previously, and derives three-dimensional wiring length which considers thickness of the wiring layer. Next, the DRC part 22 compares the three-dimensional wiring length containing height of the via and a printed pattern wiring length limit, and in the case the derived wiring length exceeds a limit value (limit length), design error information of its fact is outputted by using a DRC result output part 23. In such a way, the checking accuracy of the wiring length limit is improved.