In the adult population, psychiatric disorders and mental retardation are risk factors for foreign body ingestion. Most cases of foreign body ingestion are managed by close observation or endoscopic intervention. However, surgical intervention is mandatory in some cases. Here, we present the case of an unusually huge amount of gastric foreign bodies, which were removed by surgical intervention. A 54-year-old male patient presented with epigastric pain. He was born with mental retardation and had a 10-year history of anxiety disorder. Before the presentation, a colonic foreign body (coin) was identified 5 months ago, and the foreign body had been passed through the colon without morbidity. Plain radiography showed several foreign bodies occupying the whole stomach, and computed tomography showed multiple oval-shaped radiopaque foreign bodies in the stomach without complications. Although gastroscopy was attempted to extract these foreign bodies, it was impossible to extract all of them. Thus, surgery was performed. The foreign bodies (pebbles and coins) were extracted by surgery, and plain radiography was performed to confirm that there were no residual foreign bodies. The postoperative course was uneventful. Three months after the surgery, a radiopaque round foreign body was detected, and it was resolved without any intervention. Thereafter, the patient course was uneventful during the 1-year follow-up. Although a case with such a large number of gastric foreign bodies is extremely rare in humans, it is important to have a close follow-up after the removal of foreign bodies in patients with psychiatric disorders.