A lipopolysaccharide (LPS) and/or lipid A binding agent is provided. The LPS and/or lipid A binding agent contains an LPS and/or lipid A binding peptide, such as a peptide comprising an amino acid sequence of XYSSS (X = K, R, or H), or a derivative thereof, as an active ingredient. The LPS and/or lipid A binding agent is useful as, for example, an LPS and/or lipid A neutralizing agent or an LPS and/or lipid A removing agent.