Disclosed are: a method for activating a helper T cell,which comprises the step of adding a WT1 peptide to anantigen-presenting cell to activate the helper T cell,wherein the WT1 peptide is capable of binding to any oneselected from an HLA-DRB1*1501 molecule, an HLA-DPB1*0901molecule and an HLA-DPB1*0501 molecule; a composition foruse in the method; a therapeutic and/or prophylactic methodfor cancer by activating a helper T cell; a pharmaceuticalcomposition for use in the therapeutic and/or prophylacticmethod; and others.