A 41-year-old man with vomiting of blood was referred to our hospital. Upper gastrointestinal endoscopy revealed spurting bleeding from a submucosal tumor-like, protruded lesion in the posterior wall of the stomach. The patient was initially thought to have varices, and ligating hemostasis using an o-ring was performed. From the results of abdominal contrast computed tomography, bleeding from an enlarged left gastric artery branch that branches from the aorta was suspected. The lesion re-ruptured 11 hours later. Therefore, after performing re-ligation by the same procedure, gastrectomy and splenectomy were performed. Pathological examination revealed a change in segmental arterial mediolysis.