We report a case of Sertoli cell tumor. A 33-year-old man visited our clinic with a complaint of painless left scrotal swelling on September 29th, 2003. An elastic firm induration larger than a hen's egg in size was palpable on the surface of the left testis. Tumor markers for testicular tumor such as human chorionic gonadotropin-beta, alpha fetoprotein, and lactate dehydrogenase were not elevated. However, ultrasound showed a low echoic mass in the left testis. Therefore, we performed left high orchiectomy under the diagnosis of left testicular tumor. Its histology showed Sertoli cell tumor. Neither recurrence nor metastasis has been detected for about 8 months after the operation.