A flexible flat cable and a manufacturing method thereof are provided. The flexible flat cable includes a plurality of ground parts comprising a conductive material disposed at intervals, a plurality of signal transmission parts comprising a conductive material disposed between the plurality of ground parts, an outer skin covering the signal transmission parts and the ground parts, and a conductive adhesive layer disposed between the ground parts and the signal transmission parts and the outer skin part, the signal transmission part comprising an insulating member and a strip line disposed within the insulating member and the ground part comprising a ground member having the same cross section as the strip line and a conductive adhesive block coupled to the ground member with the conductive adhesive layer.