A wiring structure includes a main body, a first dielectric layer, a first circuit layer and a second dielectric layer. The first dielectric layer is disposed on the main body, and defines a plurality of first grooves and at least one receiving portion between two first grooves. The first circuit layer is disposed on the first dielectric layer, and includes at least one first conductive trace disposed on the receiving portion. A width of the first conductive trace is less than a width of the receiving portion. A second dielectric layer disposed on the first dielectric layer, and extends into the first grooves.