The authors report a xase of primary non-gestational choriocarcinoma(PNGCO) of the ovary in a prepubertal female patient and reviewed. It is an extremely rere disease of which incidence is one in 369 million. Major clinical symptom is abdominal pain, precociois puberty and it can be misdiagneosed as ectopic pergnancy. Distinction from gestational choriocarcinoma(GCO) of the ovary is important because of the worse prognosis of PNGCO. But no distinctive ultrastructural or immunohistochemical differences are found between PNGCO and GCO. Most acceptable treatment modality is an aggressive surgical therapy and systemic chemotherapy, but its progrosis is poor.