The present invention is to provide a non-human animal model of systemic lupus erythematosus wherein generation of anti-double stranded DNA antibody and anti-single stranded antibody is induced, and that is made to spontaneously develop glomerulonephritis and arthritis, and a screening method for a therapeutic agent for systemic lupus erythematosus wherein the non-human animal model is used. Fc.gamma.RIIB deficient mouse that is not made to spontaneously develop autoimmune pathology although its autoantibody response is enhanced is backcrossed into C57BL/6J (B6) mouse for 12 generations to generate Fc.gamma.RIIB deficient B6 mouse, the Fc.gamma.RIIB deficient B6 male mouse is intercrossed with lpr/B6 female mouse, and thus obtained Fc.gamma.RIIB.sup.+/-/lpr.sup.+/- mice were further crossed to generate a mouse model of systemic lupus erythematosus.