The utility model provides a shielding flat electric cable. Even in a high-temperature environment, the shielding flat electric cable can excellently maintain shielding performance and cannot ensuring that conducting resistance between a shielding thin film and a grounding bar increases. A plurality of flat conductors (13) are arranged in parallel and are coated by insulating thin films (14) in a clamping manner from top to bottom; one single face of the flat conductors (13) is exposed at the end part of at least one side; the shielding thin film (15) is adhered on the insulating thin films (14) of at least one side of the upper and the lower; and the grounding bar (16) is adhered on the outer surface of an end part of the shielding thin film (15) by conductive adhesive agent. A stiffening plate (17) is adhered at an end part of a side which is opposite to the side at which the flat conductors (13) are exposed; and the side at which the flat conductors are exposed is provided with the grounding bar (16) which is adhered on the outer surface of an end part of the shielding thin film. In addition, the shielding thin film (15) can cover the outer surface of the stiffening plate, (17) and then the grounding bar (16) is adhered on the shielding thin film.