Provided is a monoclonal antibody against slightly oxidized LDL, which can play a role as an important tool in the research and development of oxidized LDL. Also provided are a kit for the simple detection of slightly oxidized LDL and a method for the simple detection of slightly oxidized LDL from the biological sample of a subject to be tested which use the monoclonal antibody. By means of ELISA (Enzyme-Linked Immunosorbent Assay) using the monoclonal antibody as the solid phase antibody and an anti-apolipoprotein B antibody as the detection antibody, the degree of reaction between a severely oxidized low-density lipoprotein and the monoclonal antibody is low in comparison to the degree of reaction between a slightly oxidized low-density lipoprotein and the monoclonal antibody, and the monoclonal antibody specifically reacts with an oxidized low-density lipoprotein.