A flexible printed circuit board is disclosed, which includes a pad portion, wherein the pad portion includes a pair of first signal pads formed in a first conductor layer and respectively connected with a pair of signal wires, a pair of second signal pads formed in a second conductor layer and electrically separated from a grounding layer; a pair of first grounding pads formed in the first conductor layer and electrically separated from the pair of signal wires, wherein: the pair of first signal pads is sandwiched between the pair of first grounding pads, and a pair of second grounding pads formed in the second conductor layer and connected with the grounding layer, wherein the pair of second signal pads are sandwiched between the pair of second grounding pads. A width of the first and the second signal pads is larger than that of the signal wires.