Provided is an invention relating to a method for measuring an anti-WT1 antibody in a sample allowing measurement and evaluation of the anti-WT1 antibody with higher accuracy and to use of the method. The method for measuring an anti-WT1 antibody in a sample includes using a polypeptide having antigenicity to the anti-WT1 antibody selected from a polypeptide comprising the amino acid sequence of positions 294-449 in SEQ ID NO: 1, a partial polypeptide of the polypeptide, and a polypeptide including an amino acid sequence having deletion, substitution, or addition of one to several amino acids in the amino acid sequence constituting each of these polypeptides and/or a polypeptide having antigenicity to the anti-WT1 antibody selected from a polypeptide comprising the amino acid sequence of positions 181-324 in SEQ ID NO: 1, a partial polypeptide of the polypeptide, and a polypeptide including an amino acid sequence having deletion, substitution, or addition of one to several amino acids in the amino acid sequence constituting each of these polypeptides.
