We report a case of severe eosinophilic pneumonia induced by several antibiotics, requiring mechanical ventilation. A 44-year-old man had been admitted previously to a different hospital because of a high fever and dry cough continuing for a week. Although bacterial pneumonia was diagnosed and he had been treated with several antibiotics, his respiratory state worsened gradually and he was refered to our hospital with severe hypoxia. He needed mechanical ventilation on the fifth hospital day. TBLB identified eosinophilic pneumonia. Although we discontinued all antibiotics and started steroid therapy, he became feverish and his leukocyte count, which was neutrophil dominant, elevated again. We suspected bacterial pneumonia and administered antibiotics that he had never received before. However we had to discontinue these antibiotics soon because of a further inflammatory response. His condition then improved gradually and he was weaned from mechanical ventilation. It is rare for drug-induced eosinophilic pneumonia to become so severe that mechanical ventilation is necessary. We thought that an allergic reaction may have been induced by the series of several antibiotics, inducing severe pneumonia.