A 64-year-old man was referred to us because of pneumonia refractory to panipenem/betamipron. His chest radiography showed patchy consolidations in the lower lobe of the right lung and in the middle field of the left lung, and severe hypoxia was present. He was diagnosed as having acute respiratory distress syndrome due to severe pneumonia, and was treated with pulse methylprednisolone and sivelestat sodium in combination with intravenous erythromycin and ciprofloxacin. The patient recovered with this treatment. Serological examination using blood samples collected on the 12th and 28th hospital days revealed elevation of anti-L. pneumophila serogroup I antibody. It is suggested that administration of methylprednisolone and sivelestat sodium in combination with intravenous erythromycin and ciprofloxacin in a case of severe Legionella pneumonia complicated with acute respiratory distress syndrome is effective, and may be of use in similar cases.