An antibody which recognizes an active hepatocyte growth factor activator (HGFA) and does not substantially recognize inactive HGFA is provided. Also disclosed is a monoclonal antibody thereof, and a hybridoma cell line for producing the monoclonal antibody. There is further provided a method for measuring active HGFA using the antibody, and a method for detecting a disease, by detecting or measuring active HGFA using the antibody.