A 39-year-old man, who had been pointed out to have a lower abdominal mass, was admitted to our hospital. Physical examination revealed a child-head-sized mass with smooth surface in the middle part of the lower abdomen. Computerized tomographic scan showed the non-cystic mass located in the retroperitoneal space from the level of L5 to S5. An open biopsy was performed and pathological diagnosis was benign schwannoma (Antoni A and B type). Radical operation could not be performed because of his refusal. In addition to this case, 40 cases of retroperitoneal schwannoma reported in Japan are reviewed and discussed.