To obtain the subject new antibody comprising an antibody (or its fragment) activating erythropoietin receptor, capable of activating erythropoietin receptor and stimulating erythrocyte formation, and useful as a therapeutic agent for anaemia, or the like.

This new antibody is an antibody (or its fragment) activating erythropoietin receptor (referred to as EPOR), capable of activating erythropoietin receptor and stimulating erythrocyte formation, and useful as therapy for anaemia, diagnosis of diseases due to dysfunctional EPOR, or the like. The new antibody is obtained as an antibody for stimulating the propagation of erythropoietin-dependent cells by testing an anti-EPOR monoclonal antibody prepared through immunization of soluble human EPOR against a mouse with respect to EPOR bonds according to realtime biospecific interaction analysis (BIAcore analysis) and by screening the bonds of EPOR to the surface of transfected CHO cells according to fluorescence activated cell sorter(FACS) analysis.