A printed circuit board includes a line intensive distribution area, a line sparse distribution area, a solder mask layer, and a signal layer. A first signal line is laid on the signal layer. The first signal line crosses the line intensive distribution area and the line sparse distribution area. The first signal line is narrower in the line intensive distribution area than in the line sparse distribution area. The solder mask layer is thicker in the line intensive distribution area than in the line sparse distribution area.