An object is to produce a new anti-B7-H4 antibody having high specificity and affinity and provide a composition for treating cancer making use thereof. A monoclonal antibody that specifically binds to an extracellular domain protein of a human B7-H4 protein is newly produced and an “anti-B7-H4 antibody-effector cell complex” in which the monoclonal antibody and an effector cell are bound in order to enhance the antibody-dependent cellular cytotoxicity of the monoclonal antibody or a bispecific antibody comprising an antigen recognition region of the monoclonal antibody and an effector cell antigen recognition region is further produced and used as a composition for treating cancer.
