A method of forming solder bumps includes preparing a substrate having a surface on which a plurality of electrode pads are formed, forming a resist layer on the substrate, the resist layer having a plurality of openings, each of the openings being aligned with a corresponding electrode pad of the plurality of electrode pads, forming a conductive pillar in each of the openings of the resist layer, forming conductive layers to cover at least side walls of the resist layer in the openings to block gas emanating from the resist layer, filling molten solder in each of the openings in which the conductive layers has been formed and removing the resist layer.