The present invention relates to a flexible flat cable including a plurality of conductive wires disposed between an upper film and a lower film, in which the conductive wires are fixed by a first thermal bonding resin of the upper film and a second thermal bonding resin of the lower film, an air gap is formed between the conductive wires, and a side end of the upper film and a side end of the lower film are bonded by the first thermal bonding resin and the second thermal bonding resin, and an impedance matching sheet is attached to a lower surface of the lower film, an upper portion of the upper film, or both the upper portion of the upper film and the lower surface of the lower film.