To estimate the number of layers required for drawing wirings out of a BGA component at a high speed. A layer number estimation device includes: a bottleneck line detection means, a wiring layer adding means, and a repeating means. The bottleneck line detection means detects a line as a bottleneck line, among a plurality of lines formed by connecting electrodes, where the number of electrodes located nearer the center side than the lines is greater comparing with the number of wirings capable of passing through the lines. The wiring layer adding means disposes electrodes, among the electrodes located nearer the center side than the bottleneck line, which remain after subtracting the number of wirings capable of passing through the bottleneck line, on the next wiring layer with vias. The repeating means causes the bottleneck line detection means and the wiring layer adding means to be executed to the next wiring layer.