Poncet's disease is an aseptic polyarthritis developing in the presence of active Tuberculosis occurring elsewhere, and is not due to direct involvement of joints but to an immunological reaction to tuberculoprotein. We experienced a case of Poncet's disease accompanying erythema nodosum in a 55-year-old female patient with pulmonary tuberculosis. She had multiple tender erythematous nodules on both lower limbs for 3 months and a cough and sputum from one month ago. She felt severe pain in both knees and ankles with swelling one week before admission. Her chest X-ray, computed tomography (CT) scan and positive sputum AFB stain results revealed that she had active pulmonary tuberculosis accompanying erythema nodosum and aseptic polyarthritis. Her arthritis and erythema nodosum were dramatically improved within four weeks after anti-tuberculosis therapy. We report a case of Poncet's disease in pulmonary tuberculosis accompanying erythema nodosum.