Provided is a method that can more objectively and rapidly determine severity of pneumococcal pneumonia using blood of a subject. The method determines severity of pneumococcal pneumonia, the method including determining the severity based on the presence or absence of a pneumococcal antigen in blood collected from a subject and at least one biochemical value selected from a blood C-reactive protein (CRP) level, a white blood cell (WBC) count and a blood urea nitrogen (BUN) level.