A flex flat cable structure includes metallic transmission lines having a power line and signal lines, first insulating jackets, a second insulating jacket, a third insulating jacket, and a shield layer. Each of the first insulating jackets encloses one of the metallic transmission lines. The second insulating jacket surrounds the first insulating jackets. The third insulating jacket encloses the first insulating jackets, and the second insulating jacket encloses the third insulating jacket. The shield layer is used to isolate the second insulating jacket from the third insulating jacket. The shield layer includes an insulating film, a first block layer, and a second block layer.