A PCB includes an outer layer and an inner layer. An electronic component is mounted on the outer layer. The outer layer further defines a first pad, a second pad, a third pad, a fourth pad, and a number of via holes. The electrical performances of the first pad and the second pad are the same to that of the inner layer. The first pad and the second pad are conducted to the electronic component. The third pad and the fourth pad are respectively conducted to the first pad and the second pad through the electronic component. The electrical performances of the third pad and the fourth pad are different from that of the inner layer. The via holes are respectively electrically connected to the third pad and the fourth pad.