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.Cette invention concerne un procédé de mesure d'anticorps anti-WT1 dans un échantillon qui permet de mesurer et d'évaluer plus précisément les anticorps anti-WT1 ； et l'utilisation dudit procédé. Le procédé de mesure d'anticorps anti-WT1 dans un échantillon selon l'invention est caractérisé en ce qu'il utilise : un polypeptide ayant des propriétés antigéniques envers les anticorps anti-WT1, choisi parmi un polypeptide comprenant la séquence d'acides aminés des positions 294-449 de SEQ ID No : 1, un polypeptide partiel dudit polypeptide, et un polypeptide comprenant une séquence d'acides aminés dont un ou plusieurs acides aminés sont délétés, substitués, ou ajoutés par rapport à la séquence d'acides aminés constituant les polypeptides ci-dessus ； et/ou un polypeptide ayant des propriétés antigéniques envers les anticorps anti-WT1, choisi parmi un polypeptide comprenant la séqu
