The present invention provides a means and a method for effectively increasing Bifidobacteria in the large intestine. Specifically, the present invention relates to an agent for increasing Bifidobacteria and/or reducing the decrease of Bifidobacteria in the large intestine, which comprises spores of Bacillus subtilis and a means of delivering the spores to the large intestine of a subject while maintaining the spore form of Bacillus subtilis.
