T his invention provides a new tumor antigen having an epitope that induces a Th1 cell (a CD4-positive T cell specific to MAGE-A4), and a method of application thereof. Specifically, this invention provides a polypeptide that includes an amino acid sequence having the following characteristic a), b), c), d), e) or f) and has a cytokine-producing activity in a Th cell specific to MAGE-A4: a) An amino acid sequence represented by SEQ ID No: 1 or No: 2; b) An amino acid sequence, wherein one to several tens of any amino acids are added to N terminus and/or C terminus of an amino acid sequence represented by SEQ ID No: 1 or No: 2; c) An amino acid sequence, wherein one to five amino acids from N terminus and/or C terminus of an amino acid sequence represented by SEQ ID No: 1 or No: 2 are deleted; d) An amino acid sequence, wherein one to several amino acid residues of an amino acid sequence represented by SEQ ID No: 1 or No: 2 are substituted and/or deleted; e) An amino acid sequence, wherein one to several tens of any amino acids are added to N terminus and/or C terminus of an amino acid sequence, wherein one to several amino acid residues of an amino acid sequence represented by SEQ ID No: 1 or No: 2 are substituted and/or deleted; and f) An amino acid sequence, wherein one to several amino acid residues are substituted in an amino acid sequence, wherein one to five amino acids from N terminus and/or C terminus of an amino acid sequence represented by SEQ ID No: 1 or No: 2 are deleted.