A 68-year-old woman, presented to the emergency department with dry cough and increased shortness of breath. Her chest X-ray showed complete atelectasis of the right upper lobe. Her chest examination was significant for diffuse wheezing, and she was treated with corticosteroids. Fourteen hours after her arrival, wheezing and atelectasis on the chest X-ray disappeared. However, 10 days after admission, her chest X-ray showed atelectasis of the right lower lobe, and right middle and lower lobes atelectasis on 17 days, then became complete atelectasis of the lung on 22 days after admission. Bronchoscopic findings showed severe stenosis of the right upper lobe bronchus and truncus intermedius. Pathologic examination of the transbronchoscopic biopsy specimen showed diffuse large B-cell lymphoma. We diagnosed primary pulmonary malignant lymphoma because she had no extrapulmonary diseases. An extremely rare case of pulmonary malignant lymphoma with endobronchial involvement in which the site of atelectasis changed rapidly was reported.