A method of manufacturing a coreless package substrate together with a conductive structure of the substrate is disclosed. The method can produce a coreless package substrate which comprises: at least a built-up structure having a first solder mask and a second solder mask, wherein a plurality of openings are formed in the first and second solder mask to expose the conductive pads of the built-up structure; and a plurality of solder bumps as well as solder layers formed on the conductive pads. Therefore, the invention can produce the coreless package substrate with high density of circuit layout, less manufacturing steps, and small size.