Provided is a semiconductor package including a pair of differential signal wiring lines including a first differential signal wiring line and a second differential signal wiring line, extending parallel to and spaced apart from each other, a lower equal potential plate in a lower wiring layer under the signal wiring layer, an upper equal potential plate in an upper wiring layer above the signal wiring layer, and a wiring insulating layer adjacent to the pair of differential signal wiring lines, the lower equal potential plate, and the upper equal potential plate, the wiring insulating layer filling spaces between the signal wiring layer, the lower wiring layer, and the upper wiring layer, at least one of the lower equal potential plate and the upper equal potential plate including an impedance opening overlapping the pair of differential signal wiring lines in a vertical direction and is filled by the wiring insulating layer.