Provided is a novel butyrate-producing bacterium. A butyrate-producing bacterium belonging to Anaerostipes hadrus , wherein the amount of butyrate produced which is measured by thawing a frozen stock solution of the bacterial strain (a 10% (w/v) skim milk-2% sodium glutamate solution in which bacterial cells are suspended) (cell count: 2.0 to 5.5 × 10 10 cells/mL), inoculating 1the solution at 1% to 4 mL of a PY liquid medium supplemented with 33 mM sodium acetate and 0.5 (w/v)% glucose (PYGA medium), followed by anaerobic culture at 37°C for 24 hours, then inoculating the culture solution at 1% to a PYGA medium, followed by anaerobic culture at 37°C for 24 hours, then inoculating the culture solution at 1% to a PY medium containing 33 mM sodium acetate and 0.5 (w/v)% L-sorbose, followed by anaerobic culture at 37°C for 24 hours, and then measuring the butyrate concentration in the culture solution is at least 1.5 times that of Anaerostipes hadrus ( Eubacterium hadrum ) YIT 10092 T (DSM 3119 T ), which is a type strain of Anaerostipes hadrus ( Eubacterium hadrum ) .