A wiring design apparatus for designing a plurality of wiring lines of a printed circuit board including a plurality of connection posts arranged in a matrix, includes a processor, the processor providing an orthogonal grid including a plurality of rows and columns running over and between the connection posts, providing a plurality of diagonal paths each connecting at least one of the rows with at least one of the columns each running between each of adjacent pairs of the connection posts, and determining a route for each of the wiring lines by exclusively allocating to each of the wiring lines a selected part of the rows, the columns and the paths so that the selected part connects both ends of each of the wiring lines.