A flexible printed circuit board (FPCB) includes at least one signal pad part disposed at each of a top and bottom of a flexible substrate base and configured to include an upper signal pad and a lower signal pad and a through hole formed at a portion corresponding to a signal via, a signal line disposed at the top of the substrate base, and extending from the upper signal pad along a length direction of the substrate base, an upper ground pad disposed at the top of the substrate base to be separated from the upper signal pad and the signal line near the upper signal pad, and a lower ground pad disposed at the bottom of the substrate base to be separated from the lower signal pad near the lower signal pad, and connected to the upper ground pad through a ground via.