Castleman’s disease, giant lymph node hyperplasia, is a kind of benign lymphoproliferative disease with gentle behavior. Its etiology and prevalence are unclear. This rare disease is usually found in mediastinal area asymptomatically and incidentally. It is also rare to see this tumor in the retroperitoneum. In this study, we have introduced a 34-year-old woman who referred just with occasional abdominal pain caused by compressive symptoms. Laboratory findings only reported microcytic anemia (MCH: 18.5, MCV: 63, Hemoglobin 10.2 g/dl). Chest and abdominal X-ray imaging showed no remarkable point. In abdominal ultrasonography, a solid and firm tumor with 12.2×5.3×6.6 cm was reported in patient’s retroperitoneum. Patient’s surgery was done and the tumor (covered by a fibrous thick capsule, with no bizarre appearance and bleeding) was completely removed. Pathologic examination indicated a Castleman’s tumor, type of unicentric and hyaline-vascular. This item had been one of the rare reported items of Castleman’s disease in the retroperitoneal space.