A circuit board structure comprising a composite layer, a fine circuit pattern and a patterned conductive layer is provided. The fine circuit pattern is inlaid in the composite layer, and the patterned conductive layer is disposed on a surface of the composite layer. After fine circuit grooves are formed on the surface of the composite layer, conductive material is filled into the grooves to form the fine circuit pattern inlaid in the composite layer. Since this fine circuit pattern has relatively fine line width and spacing, the circuit board structure has a higher wiring density.