A 40-year-old man was admitted to our hospital because of chronic cough and mild exertional dyspnea. Radiographs of the chest showed diffuse infiltrative shadows in both lung fields. A diagnosis of pulmonary alveolar proteinosis (PAP) was made by examination with a flexible bronchoscope and bronchoalveolar lavage, with transbronchial biopsy. After diagnosis, the patient underwent whole-lung lavage with temporary improvement. Due to the recurrence of his illness, he needed a total of four whole-lung lavages over the course of his illness. However, the exertional dyspnea became progressively worse. Bilateral pneumothorax developed suddenly and led to his death. This case indicates the possibility that deterioration of PAP despite whole-lung lavage may sometimes be followed by pneumothorax.