Primary choriocarcinoma of the lung is extremely rare. The patient was 28-year-old female and had no specific signs and symptoms except right chest pain for 5 years. On simple chest film, 8X8 cm sized, well demarcated, homogeneous ovoid mass was found on right lower lung field. The qualitative urine ulcorner-HCG was 17140 mIU/ml. The result of percutaneous needle biopsy highly suggested choriocarcinoma. Under the impression of primary choriocarcinoma of the lung, right middle and lower lobectomy was done. On 33 postoperative days, serum ulcorner-HCG level was within normal limit, the patient was discharged without complications after one-cycle chemotherapy.