Patients with microscopic polyangiitis may have an immune disorder and generate antibodies which may cross-react with foreign proteins. In this article, we report a 71-year-old female case of microscopic polyangiitis patient with positive Hantaan virus-specific immunoglobuline M antibodies without hemorrhagic fever with renal syndrome. In this case, an immune disorder may generate antibodies that cross-reacting with Hantaan virus antigen, resulting in positive Hantaan virus-specific immunoglobuline M antibody measurements.