A welding method for an impeller having a plurality of blades, a disc and an exterior body including a shroud welded to the plurality of blades, comprising the steps of: a first step for forming a groove having a prescribed depth and a prescribed width toward one of the blades on a surface of the disc or the exterior body, which is opposite to a surface against the blade abuts, emitting laser light toward the bottom of the groove, and performing melt-through bead welding to bond the bottom of the groove to an end of the blade in such a way that a bead formed on the back of the disc or the shroud is curved with an inward depression; and a second step for performing overlaying welding after completion of the first step by supplying a filler metal to a molten zone while the bottom of the groove is scanned with the laser light.