We report a rare case of hypereosinophilic syndrome (HES) presenting with intractable gastric ulcers. A 71-year-old man was admitted with epigastric pain. Initial endoscopic findings revealed multiple, active gastric ulcers in the gastric antrum. He underwent Helicobacter pylori (H pylori) eradication therapy followed by proton pump inhibitor (PPI) therapy. However, follow-up endoscopy at 4, 6, 10 and 14 mo revealed persistent multiple gastric ulcers without significant improvement. The proportion of his eosinophil count increased to 43% (total count: 7903/mm3). Abdominal-pelvic and chest computed tomography scans showed multiple small nodules in the liver and both lungs. The endoscopic biopsy specimen taken from the gastric antrum revealed prominent eosinophilic infiltration, and the liver biopsy specimen also showed eosinophilic infiltration in the portal tract and sinusoid. A bone marrow biopsy disclosed eosinophilic hyperplasia as well as increased cellularity of 70%. The patient was finally diagnosed with HES involving the stomach, liver, lung, and bone marrow. When gastric ulcers do not improve despite H pylori eradication and prolonged PPI therapy, infiltrative gastric disorders such as HES should be considered.