Choriocarcinoma is rare and aggressive tumor with high metastastic potential. During intrauterine pregnancy, incidence of choriocacinoma is more rare, 1 in 1.6 million. Futhermore, there are limitations to diagnose choriocarcinoma if a patients has unsual symtopms and signs. A 40-year-old nullipara woman at the 18th gestational week transferred with intermittent low abdominal pain. Ultrasound showd normal fetal anatomy and huge solid mass in left abdomen. Also futher MRI examination showed a 9.5cm sized solid mass looking like uterine myoma in left side uterus. Cesarean section was performed at the 23th gestational weeks due to uncontrolled acute abdomen and early onset preeclampsia symptoms. Final histology of solid mass in left side uterus was metastastic ovarian choriocarcinom. Choriocarcinoma is potentially fatal when diagnosis is delayed. It can present in unusual ways, as in this case. Here we present this case to help that clinician make decision in the early diagnosis and management of this potentially curable life-threatening disease.