[Problem] The purpose of the present invention is to provide a device for the prophylaxis and treatment of systemic lupus erythematosus, a method for use as a biomarker of systemic lupus erythematosus, and a method for determining systemic lupus erythematosus. [Solution] The prophylaxis/treatment of systemic lupus erythematosus is characterized by reducing the concentration of Hsp90 in the blood, the serum, or the blood plasma of a subject by using a substance capable of removing Hsp90. The method for use as a biomarker of systemic lupus erythematosus is characterized by using Hsp90 in the blood, the serum, or the blood plasma of a subject as a biomarker. The method for determining systemic lupus erythematosus is characterized by comparing and evaluating the concentration of Hsp90 in the blood, the serum, or the blood plasma of a subject with/against that of a normal control.
