Abstract: KGF-C is obtained by grinding kefir grain, adding water to the ground kefir grain and heating, homogenizing the mixture and centrifuging it, adding ethanol to the obtained supernatant to obtain a precipitate, dissolving the precipitate into water, purifying the obtained liquid and freeze-drying the remaining liquid. The obtained KGF-C is soluble in water and is composed of polysaccharide as principal component and contains a very small amount of nitrogenous component, and, as sugar composition, is composed of glucose and galactose in the ratio 1:1. This KGF-C has strong antitumor action by oral administration.