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