A method for fabricating a conductive via structure is provided, which includes the steps of: forming in an encapsulant a plurality of openings penetrating therethrough; forming a dielectric layer on the encapsulant and in the openings of the encapsulant; forming a plurality of vias in the dielectric layer in the openings of the encapsulant; and forming a conductive material in the vias to thereby form conductive vias. Therefore, by filling the openings having rough wall surfaces with the dielectric layer so as to form the vias having even wall surfaces, the present invention improves the quality of the conductive vias.