We report a case of a 38-yr-old man with a spontaneously ruptured gastric stromal tumor presenting as hemoperitoneum in outpatient clinic. He visited our hospital with generalized abdominal pain after abdominal CT scan for the evaluation of the asymptomatic palpable abdominal mass. Repeated abdominal CT scan showed a size decrement of cystic mass compared with the previous abdominal CT scan, and newly developed fluid collection in the left paracolic gutter. An emergency laparotomy revealed a ruptured gastric stromal tumor with bloody fluid in the peritoneal cavity. Immunohistochemical examination revealed positive reactivity to C-kit protein and CD34. The patient presented with hemoperitoneum due to spontaneous rupture of the tumor, which is an extremely rare complication.