The object of the present invention is to provide an anti-tumor agent having an anti-angiogenic effect and/or an anti-tumor growth effect or a method for tumor growth inhibition.The present invention provides an anti-tumor agent characterized by having an anti-angiogenic effect and/or an anti-tumor growth effect, which contains a polypeptide of galactosylceramide expression factor-1 excluding the Q region, wherein the polypeptide comprises at least the C region or a part thereof.