The present invention provides a disinfectant that containsolanexidine in a concentration sufficient to exhibit an effectivebactericidal effect, and that has hardly any side effects such asskin irritation. Specifically, the present invention provides adisinfectant containing an aqueous solution that containsolanexidine and at least an equimolar amount of gluconic acid,and substantially contains neither an acid other than gluconicacid nor a salt of the acid other than gluconic acid.