An object of the present invention is to provide an agent for decomposing an opioid peptide or composition for decomposing an opioid peptide that does not restrict dietary habits, does not provide side reactions, even if it is daily used, and thus can be continuously used without any worries. The object is achieved by an agent for decomposing an opioid peptide or composition for decomposing an opioid peptide, pharmaceutical composition for decomposing an opioid peptide, or food or drink composition for decomposing an opioid peptide containing a Bifidobacterium bacterium, a culture of the bacterium, and/or a processed cell product of the bacterium as an active ingredient.
