Gastric necrosis due to gastric outlet obstruction is a very rare condition, but it might be fatal if missed or if diagnosis is delayed. Our patient was a 73-year-old male complaining of abdominal pain, distension and dyspnea for 1 day. In plain radiography and computed tomography, a markedly distended stomach and decreased enhancement at the gastric wall were noted. He underwent explo-laparotomy, and near-total gastric mucosal necrosis accompanied by sludge from the soaked laver was noted. A total gastrectomy with esophagojejunostomy was performed, and he recovered without sequelae. Final pathologic examination revealed advanced gastric cancer at the antrum with near-total gastric mucosal necrosis.