An object of the present invention is to provide a novel malignant glioma antitumor agent and malignant glioma antitumor agent for animals, and in order to achieve this object, in the present invention a polypeptide indicated by the following (a) or (b), or a mixture thereof, is contained in a malignant glioma antitumor agent: (a) a polypeptide comprising the amino acid sequence represented by SEQ. ID NO. 1 or SEQ. ID NO. 2; or (b) a polypeptide comprising the amino acid sequence represented by SEQ. ID NO. 1 or SEQ. ID NO. 2 with 1 or more amino acids deleted, substituted or added, and which has malignant glioma antitumor action.