A method of fabricating a circuit board includes the following steps. A first and a second patterned conductive layer are plated on the first and the second surface of a core substrate, respectively. A first and a second extending pad are individually plated on a first and a second pad of the first and the second patterned conductive layer, respectively. A first and a second thermal-curing type dielectric layer are individually formed on the first and the second surface to cover the first and the second patterned conductive layer and the first and the second extending pad, respectively. A portion of the first and the second thermal-curing type dielectric layer respectively covering the top of the first and the second extending pad are removed. A protective film covers the second extending pad. The extending pad is removed by an etching process.