PROBLEM TO BE SOLVED: To provide an anti-fatigue composition that has effects of inhibiting lactate production and blood lactate accumulation and excels in improvement of stamina.SOLUTION: This anti-fatigue composition contains, as an active component, a fermented composition obtained by inoculating Bacillus natto into a medium that contains brans and soybeans and carrying out fermentation and culturing. The anti-fatigue composition is usable as an inhibitor of lactate production and/or a blood lactate accumulation.