A conductive bump structure of a circuit board and a method for forming the same are proposed. A conductive layer is formed on an insulating layer on the surface of the circuit board. A first resist layer is formed on the conductive layer and a plurality of first openings is formed in the first resist layer to expose the conductive layer. Then, a patterned trace layer is electroplated in the first openings and a second resist layer is covered on the circuit board with the patterned trace layer. Second openings are formed in the second resist layer to expose part of the trace layer to be used as electrical connecting pads. Thereafter, metal bumps are electroplated in the second openings and the surface of the circuit board is covered with a solder mask. A thinning process is applied to the solder mask to expose the top surface of the metal bumps. Afterwards, an adhesive layer is formed on the surface of the metal bumps exposing out of the solder mask.