PROBLEM TO BE SOLVED: To provide an intestinal butyric acid production bacterium increasing agent.SOLUTION: This intestinal butyric acid production bacterium increasing agent includes the spore of Bacillus subtilis having a capacity of increasing butyric acid production bacteria in an animal gut or mixed bacteria of the spore and germination bacteria or a germination bacterial cell as active ingredients. Further, food, feed or medicine includes the intestinal butyric acid production bacterium increasing agent.