A residue-removing solution for removing residues present on semiconductor substrates after dry etching and/or ashing, the residue-removing solution comprising a Cu surface protective agent including: at least one compound selected from compounds (1), (2) and (3) each having as a basic skeleton a five-membered or six-membered heteratomic structure as defined herein; a compound capable of forming a complex or chelate with Cu (copper); and water. Further, the residue-removing solution has a pH of 4 to 9.