The present invention addresses the problem of providing an agent for degrading an opioid peptide or a composition for degrading an opioid peptide which requires no restriction on diet, shows no side effects even if used regularly and, therefore, can be continuously used free from anxiety. To solve this problem, provided are an agent for degrading an opioid peptide, a composition for degrading an opioid peptide, a medicinal composition for degrading an opioid peptide and a food or beverage composition for degrading an opioid peptide, each comprising, as an active ingredient, a bacterium belonging to the genus