The present invention provides a cover film for a printed circuit board. The cover film includes an adhesive layer; a core layer made of a polymer; and a composite material layer formed on the core layer, comprising epoxy resin, a black material selected from the group consisting of a black pigment, carbon powder, nano carbon tube and a combination thereof, and an additive selected from the group consisting of titanium dioxide, boron nitride, barium sulfate and a combination thereof, wherein the core layer is disposed between the adhesive layer and the composite material layer, and the adhesive layer and the composite material layer have the same thickness or have a thickness difference being no more than 15 micro meters. The cover film of the preset invention is capable of shielding circuit patterns and has great folding endurance, and is thus applicable to flexible printed circuit boards.