An impedance matching method includes following operations: providing load impedance data of a network interface controller chip; providing characteristic data of a network transformer, in which the network transformer is configured to be connected to the network interface controller chip via a transmission line on a printed circuit board, and a first predetermined data rate of the network transformer is lower than a second predetermined data rate of the network interface controller chip; adjusting an arrangement among the load impedance data, a length of the transmission line, and a width of the transmission line according to the characteristic data to adjust an impedance matching between the network transformer and the network interface controller chip, in order to make the network transformer meet a predetermined requirement corresponding to the second predetermined data rate; and storing the arrangement to be design data for fabricating the printed circuit board.