A method for manufacturing a substrate for a semiconductor package includes the steps of attaching first and second insulation layers which have first surfaces and second surfaces and are formed with conductive layers on the first surfaces, by the medium of a release film which has adhesives attached to both surfaces thereof, such that the second surfaces of the first and second insulation layers face each other; forming first conductive patterns on the first surfaces of the first and second insulation layers by patterning the conductive layers; forming solder masks on the first surfaces of the first and second insulation layers including the first conductive patterns to open portions of the first conductive patterns; and separating the first and second insulation layers from each other by removing the release film.