Provided is a method for predicting a clinical effect on a subject in a WT1 peptide immunotherapy, said method comprising: a) a step for contacting a sample derived from the subject with WT1 antigen peptide or a variant thereof； and b) a step for detecting the binding of the sample to the WT1 antigen peptide or a variant thereof and thus measuring anti-WT1 antigen peptide IgG antibody titer existing in the sample, characterized in that an increase in the anti-WT1 antigen peptide IgG antibody titer in the subject determines the achievement of a favorable clinical effect. Also provided is a kit for performing the method according to the present invention, said kit containing WT1 antigen peptide or a variant thereof.
