A 26-year-old man was admitted to our hospital because of a high-grade fever and abdominal pain. A blood test showed marked inflammation. Enhanced computed tomography (CT) showed an 8.0×6.0cm cystic lesion in the left hepatic lobe. Esophagogastroduodenoscopy showed a huge egg-yolk-like mass in the gastric submucosa in the lesser curvature of the gastric body from the gastric angle. There were 3 ulcers on the mass, out of which milky pus flowed. Trophozoites of Entamoeba histolytica were detected from cultures of the liver abscess and a biopsy of the gastric ulcers. The amoebic dysentery antibody titer was increased 1600 times. An amoebic liver abscess complicated by a gastric fistula was diagnosed. As therapy, oral metronidazole was administered for 2 weeks without percutaneous drainage. The systemic inflammatory findings improved immediately and the abscess decreased markedly in size.