To provide a composition for treating, preventing, improving, inhibiting cancer or inhibiting its metastasis, which can be used as a supplement (food) and has excellent anti-cancer action and anti-metastasis action.SOLUTION: The present invention provides a composition for treating, preventing, improving, inhibiting cancer or inhibiting its metastasis, which contains a plant fermentation extract as an active ingredient, the plant fermentation extract containing the yeast which can survive in an environment of pH 1 and shows a spore forming ability in a complete medium.SELECTED DRAWING: None