A 69 year-old man was admitted to our hospital with bloody sputum and abnormal shadows in his chest X-ray film and CT. According to the bronchoscopic examination, he was diagnosed as suffering from small cell lung cancer (SCLC). Aside from SCLC, erythroderma, lymphoadenopathy and abnormal lymphoid cells in his peripheral blood were recognized on admission. Considering possible disorder blood complications, we conducted examinations including a biopsy of the skin and superficial lymph nodes, which revealed the characteristics of Sézary syndrome. We provided local treatment for Sézary syndrome and did systemic chemotherapy with carboplatin and etoposide for SCLC. After four cycles of chemotherapy, the patient showed a partial response. We report a very rare case of SCLC with Sézary syndrome in which we were able to provide chemotherapy effectively and safely.