An object of the present invention is to provide a measurement method and a reagent for measurement which can measure LRG in a biological sample simply in a short time. The present inventors have intensively studied to achieve the object and made findings that LRG in a biological sample can be measured simply in a short time by an immunoagglutination measurement method in which the biological sample is brought into contact with insoluble carrier particles carrying a first anti-LRG monoclonal antibody and insoluble carrier particles carrying a second anti-LRG monoclonal antibody in a liquid phase, and the invention has been thus completed.