A 45-year-old man with steroid-dependent ulcerative pancolitis was hospitalized with frequent diarrhea, abdominal pain and distension 3 months after induction of golimumab, a tumor necrosis factor-alpha antagonist. Computed tomography showed wall thickening from the stomach to the colon and massive ascites. Peripheral blood test revealed eosinophilia. A large number of eosinophils were observed in the ascites fluid. Although esophagogastroduodenoscopy showed no abnormal findings and colonoscopy showed ulcerative colitis with a Mayo endoscopic subscore of 1, eosinophil infiltration was histologically observed. Based on these findings, we diagnosed him with eosinophilic gastroenteritis and started prednisolone. Consequently, his eosinophil counts and abdominal symptoms dramatically improved.