A diffuse alveolar hemorrhage is a rare manifestation in microscopic polyangiitis. Recently we experienced a case of diffuse alveolar hemorrhage associated with microscopic polyangiitis, which was diagnosed with the typical clinical manifestations, ANCA and a renal biopsy. A 71 year old female was admitted complaining of coughing and dyspnea. A chest X-ray, HRCT and BAL revealed a diffuse alveolar hemorrhage. A diffuse alveolar hemorrhage was noted during a bronchoscopy. She also had proteinuria, microscopic hematuria and mild azotemia. The renal biopsy showed necrotic glomerulonephritis without immune complex deposits or granuloma. Under the diagnosis of microscopic polyangiitis, she was treated with steroid pulse therapy, and prednisolone with cyclophosphamide subsequently. She showed marked improvement in the clinical manifestations.