We encountered a patient with giant ovarian cancer with a tumor weight of 100 kg. The patient's girth measured 198 cm after approximately 4 years' duration, and she complained of dyspnea and inability to walk. Adnectomy was performed with intensive intraoperative monitoring. The ovarian cancer was entirely adherent to the parietal peritoneum. However, 10 h after adnectomy, she died of massive abdominal bleeding from extremely redundant parietal peritoneum caused by disseminated intravascular coagulation.