A 28-year-old woman was admitted to our hospital complaining of a 7-day chilly sensation with fever. She was given a diagnosis of pneumococcal pneumonia because of infiltration on chest radiography, sputum gram staining and testing positive for a pneumococcal urinary antigen. A 10-day course of antibiotics showed improvements in symptoms and infiltration. However, her X-ray film revealed severe volume loss in the right lung. Organizing pneumonia was diagnosed with lymphocytosis in BALF and Masson bodies upon TBLB examination. Administration of prednisolone obtained rapid improvement of the volume loss. This case was interesting, showing an organizing tendency in the acute-stage pneumococcal pneumonia.