In connective tissue diseases, autoantibodies cause pulmonary interstitial inflammation and fibrosis, and patients require treatment with an immunosuppressive agent such as a steroid. Dermatomyositis is an incurable, uncommon form of connective tissue disease that occasionally causes diffuse pulmonary inflammation leading to acute severe respiratory failure. In such cases, the prognosis is very poor despite treatment with high-dose steroid. In the present case, a 46-year-old man was admitted to our hospital with dyspnea. He was diagnosed with dermatomyositis combined with cryptogenic organizing pneumonia (COP) with respiratory failure and underwent treatment with steroid and an immunosuppressive agent, but the COP was not improved. However, the respiratory failure did improve after treatment with intravenous immunoglobulin, which therefore can be considered a treatment option in cases where steroids and immunosuppressive agents are ineffective.