A circuit substrate comprises a first circuit level, a second circuit level, a first reference plane, a second reference plane, a first communicating hole and a second communicating hole. Both of thefirst circuit and the second circuit are respectively provided with a first signal line and a second signal line. A first connecting hole is positioned between the first circuit level and the second circuit level for connecting the first signal line and the second signal line. A second connecting hole is positioned between the first reference plane and the second reference plane for connecting thefirst reference plane and the second reference plane; wherein, the second connecting hole winds around the periphery of the first connecting hole.