The present invention provides a method of fabricating a circuit substrate. First, a substrate having first pads and second pads is provided, wherein the first pads and second pads are arranged respectively on a first surface and a second surface of the substrate. The first pads are electrically connected to the second pads. Next, a conductive seed layer is formed on the second surface of the circuit substrate. Thereafter, a first conductive layer and a second conductive layer are electroplated respectively over the first pads and the second pads. Afterwards, the conductive seed layer is patterned.