A 65-year-old man was admitted due to rapidly progressing dyspnea experienced over a 3-day period. Chest radiography and computed tomography conducted upon admission showed diffuse bilateral interstitial infiltrate. Bronchoalveolar lavage fluid contained blood and siderophores, which suggested pulmonary alveolar hemorrhage. Laboratory data showed that the serum MPO-ANCA level was elevated, and so ANCA-associated pulmonary hemorrhage was diagnosed. Although aggressive immunosuppressive agents were administered, including steroids and cyclophosphamides, the patient's condition worsened. Plasmapheresis using fresh frozen plasma was performed on day 5, after which his symptoms improved dramatically. Plasmapheresis was done 6 times, and the pulmonary lesions resolved. The patient was discharged 6 months later. This case report suggests that plasmapheresis may be an effective treatment for ANCA-associated vasculitis with diffuse alveolar hemorrhage that is resistant to aggressive immunosuppressive therapy.