Abstract Objectives: Polymyositis is non-hereditary, autoimmune rheumatic disease, and one of the idiopathic inflammatory myopathy. It is characterized by progressive symmetrical proximal muscle weakness. Major clinical signs and symptoms of polymyositis are chronic non-suppurative inflammatation of skeletal muscle, elevation of muscle enzyme, and electromyographical changes. By use of Korean medicine treatments, muscle weakness and normalize muscle enzyme can be improved in case of polymyositis. Methods: A Patient, 32 years old, whom diagnosed with polymyositis on muscle biopsy and electromyographical changes, had medical treatments with Corticosteroids and Immunosuppressants, but no improvement was noted. She was treated with Korean Medicine, especially Ohaeng-Hwa Acupuncture(五行和鍼法) and Ssanghwa-Tang(雙和湯) for three months period. Results: With Korean Medicine treatment of polymyositis for three months, most of her clinical signs and symptoms have been improved significantly, especially her muscle weakness and muscle enzyme level. Conclusion: This case has been reported to show that Korean medicine treatments have positive effects on polymyositis.