A circuit structure of a circuit board includes a dielectric layer, a number of first circuits, and a number of second circuits. The dielectric layer has a surface and an intaglio pattern. The first circuits are disposed on the surface of the dielectric layer. The second circuits are disposed in the intaglio pattern of the dielectric layer. Line widths of the second circuits are smaller than line widths of the first circuits, and a distance between every two of the adjacent second circuits is shorter than a distance between every two of the adjacent first circuits.