A flexible electronic device including a flexible substrate, a plurality of first signal lines, a plurality of first transmission lines, a plurality of first through holes, and a plurality of first conductive structures is provided. The flexible substrate has a first surface and a second surface opposite to the first surface. The first signal lines are located on the first surface and have a first extending direction. The first transmission lines are located on the second surface and have a second extending direction. A first included angle is provided between the first extending direction and the second extending direction. An angle of the first included angle is between 10° and 80°. The first through holes penetrate through the flexible substrate. The first conductive structures are located in the first through holes and are electrically connected to the first signal lines and the first transmission lines.