Provided is an invention relating to a method for measuring anti-WT1 antibodies in a sample according to which the anti-WT1 antibodies can be measured and evaluated more accurately； and to use of the method. A method for measuring anti-WT1 antibodies in a sample, characterized in using: a polypeptide having antigen properties against anti-WT1 antibodies, selected from a polypeptide comprising an amino acid sequence of positions 294-449 in SEQ ID NO: 1, a partial polypeptide of said polypeptide, and a polypeptide comprising an amino acid sequence in which one or several amino acids are removed, replaced, or added with respect to the amino acid sequence constituting the above polypeptides； and/or a polypeptide having antigen properties against anti-WT1 antibodies, selected from a polypeptide comprising an amino acid sequence of positions 181-324 in SEQ ID NO: 1, a partial polypeptide of said polypeptide, and a polypeptide comprising an amino acid sequence in which one or several amino acids are removed, replaced, or added with respect to the amino acid sequence constituting the above polypeptides.
