Sclerosing stromal tumor (SST) is a rare ovarian neoplasia deriving from the sex cord stromal tumor, which occurs usually in the second and third decades of life. However, the authors report a 46-year old multiparous woman who presented with a cystic-solid left pelvic mass, a large amount of ascites, and elevated serum CA-125, all suggesting a malignant tumor. Surgery was performed and final histopathological diagnosis of the specimen was diagnosed with SST. The authors herein report an extremely rare case of SST with a cystic-solid pelvic mass and a large amount of ascites, which is useful to demonstrate the possibility of SST in multiparous woman.