Case Study: Idiopathic hypereosinophilic syndrome is a rare disorder characterized by hypereosinophilia(more than 1,500/mm3 at least twice every 4 weeks on peripheral blood tests) and damage to multi-organ, which include lungs, heart, skin, nervous system, and gastrointestinal(GI) tract. However, in the event of organ damage that requires immediate treatment, diagnosis is possible regardless of the duration. Idiopathic hypereosinophilic syndrome in hemodialysis patients is reported as a case report or series. We report a case in which severe intradialytic hypotension and uncontrolled GI symptoms were treated using steroids in hemodialysis patients with idiopathic hypereosinophilic syndrome. A 69-year-old male patient was admitted for intradialytic hypotension, fever, abdominal pain and diarrhea. He had been undergoing hemodialysis for 30 months. The cause of his renal disease was unknown. Previously he had hypertension, gout, benign prostate hyperplasia and psoriasis. He had been treating severe gastric and duodenal ulcers. At the time of hospitalization, antibiotics(ceftazidime and metronidazole) were administered because fever and an increased CRP were observed, and infection could not be excluded. Clostridium difficile Ag was identified in the stool test. And clostridium infection and enterocolitis were diagnosed and treated. However, despite antibiotic treatment, his symptoms did not improve at all. Due to intradialytic shock, CRRT(continuous renal replacement therapy) was performed and his symptoms such as GI symptoms, intradialytic hypotension and post-dialytic fever improved during CRRT. After switching to conventional hemodialysis, similar symptoms occurred again, and consistent eosinophilia was observed. Although all drugs except anti-hypertensive drugs and PPI(proton-pump inhibitor) were stopped and dialysis membranes, blood flow rates, and dialysate flow rates were adjusted, his symptoms and eosinophilia did not improve. Idiopathic hypereosinophilic syndrome was diagnosed and steroid 0.5mg/kg/day was administered. Within one day of administration, his symptoms improved, and dialysis became possible. Currently, his symptoms have completely improved, and low dose steroid has been maintained.