[Problem] To provide a substance and method that are capable of effectively inducing proliferation in bacteria of the genus Faecalibacterium, thereby contributing to the prevention and treatment of diseases such as enterocolitis. [Solution] A proliferative agent for bacteria of the genus Faecalibacterium that contains 1-kestose as an active ingredient. In accordance with the present invention, proliferation can be effectively induced in bacteria of the genus Faecalibacterium both in vitro and in vivo. In particular, it is possible to simply and effectively increase in vivo proliferation of bacteria of the genus Faecalibacterium in humans and animals, with almost no concerns regarding side effects or safety. It is also possible to prevent or treat enterocolitis by increasing in vivo proliferation of bacteria of the genus Faecalibacterium in humans and animals.
