A 71-year-old woman was diagnosed as having multiple myeloma (IgG λ type) in June 2007. A cough developed in December 2008 that had slowly worsened. It developed again in September 2010, along with bloody sputum and dyspnea on exertion, and she presented to our hospital in April 2011. Chest high-resolution computed tomography revealed diffuse ground-glass opacities, reticular shadows, and thickening of the interlobular septum. The diffuse ground-glass opacities were diagnosed as pulmonary hemorrhage by bronchoalveolar lavage on admission. After pulmonary hemorrhage resolved, transbronchial lung biopsy showed a deposition of eosinophilic amorphous material in the alveolar septa and blood vessel walls. Rectal membrane tissue showed deposition of amyloid protein, and cardiac amyloidosis was suspected on the basis of echocardiographic and heart catheterization findings. After diuretics and chemotherapy (melphalan + prednisolone) were started, her symptoms and pulmonary and cardiac amyloidosis did not develop further. She was followed up on an outpatient basis. Diffuse alveolar septal amyloidosis is often asymptomatic and is rarely diagnosed antemortem. When respiratory symptoms are present in multiple myeloma patients, pulmonary hemorrhage and amyloidosis should be considered.