Disclosed herein is a flat uniform transmission line having an electromagnetic shielding function. The flat uniform transmission line includes a strip transmission line, an insulating layer, and electromagnetic shielding layers. The strip transmission line is formed on a dielectric layer made of functional polymer material, and includes a plurality of strip lines. The plurality of strip lines are configured to be a ground line, or to transmit signals. The insulating layer is formed on the strip transmission line. The electromagnetic shielding layers are respectively formed on the insulating layer and beneath the strip transmission line.