An exemplary printed circuit board includes a substrate, a differential transmission line, and at least two weld pad pairs. The differential transmission line and the at least two weld pad pairs are disposed on the substrate. The differential transmission line includes two parallel signal conductors disposed on the substrate. Each of the two signal conductors is electrically connected to an edge of one of the weld pads of a respective pair of the at least two weld pad pairs. Thereby, the two signal conductors of the differential transmission line can extend in the same distance anywhere, particularly in the position where the two signal conductors pass the two weld pad pairs. As a result, the coupling performance and the capability of the differential transmission line to resist electromagnetic interference are both enhanced.