1. A circuit board comprising:a first conductive layer;
a second conductive layer; and
an insulating layer disposed between the first conductive layer and the second conductive layer,
wherein the first conductive layer comprises a signal line, the second conductive layer comprises a ground line electrically separated from the signal line, in a corresponding area provided with the signal line and the ground line, the ground line is patterned, and
wherein an outer unit pattern of the ground line is substantially parallel to the signal line and an inner unit pattern of the ground line is oblique to the signal line.