A 70-year-old Japanese man was re-admitted because of relapse of adenocarcinoma of the lung. He received daily administration of gefitinib as second-line chemotherapy. He was given a diagnosis of drug-induced lung disease due to gefitinib on day 6 because of hypoxemia and ground glass opacities in the bilateral lung fields. There was no response to corticosteroid pulse therapy. Continuous administration of sivelestat was intravenously added from day 9. Although mechanical ventilation was required for 10 days, lung infiltrates and hypoxia gradually improved. Sivelestat and corcicosteroid was apparently effective in this case and may be useful treatment for drug-induced lung disease due to gefitinib.