Provided are a circuit board structure and a fabrication method thereof, including the steps of: forming a first circuit layer in a first dielectric layer and exposing the first circuit layer therefrom; forming a second dielectric layer on the first dielectric layer and the first circuit layer, and forming a second circuit layer on the second dielectric layer; forming a plurality of first conductive vias in the second dielectric layer for electrically connecting to the first circuit layer to thereby dispense with a core board and electroplated holes and thus facilitate miniaturization. Further, the first dielectric layer is liquid before being hardened and is formed on the first dielectric layer that enhances the bonding between layers of the circuit board and the structure.