PROBLEM TO BE SOLVED : To provide an intestinal bacterial flora improver, preferably an intestinal bacterial flora improver that can be used for reducing the ratio of Firmicutes bacteria to Bacteroidetes bacteria in the intestinal bacterial flora.SOLUTION : An intestinal bacterial flora improver contains Euglena and is used for reducing the ratio of Firmicutes bacteria to Euglena gracilis Bacteroidetes bacteria.EFFECT : The intestinal bacterial flora improver has a reduced side effect and can be taken for a long period of time.SELECTED DRAWING : NoneCOPYRIGHT : (C)2019, JPO&INPIT