This invention provides an anti-HLA-DR monoclonal antibody. This invention relates to an antibody binding to HLA-DR or a functional fragment thereof having (a) life-extending effects in nonhuman animals bearing HLA-DR-expressing cancer cells and (b) activity of suppressing immune responses lower than that of L243, or an antibody binding to HLA-DR or a functional fragment thereof exhibiting immunosuppressive activity equivalent to or higher than that of the mouse anti-HLA-DR monoclonal antibody L243 (ATCC HB-55).