Recently, we have experienced a case of spontaneous rupture of the left iliac vein in a 62-year-old woman, who had been suffering from hemiparesis and chronic constipation. An urgent laparotomy was performed for massive hemoperitoneum without knowing the bleeding point, and laceration on the left external iliac vein was repaired. Spontaneous rupture of the iliac vein is extremely rare. However, it should be included in differential diagnoses of the patient with massive hemoperitoneum who have no known pathology or any evidence of blunt trauma.