Inclusion Criteria:  Patients with Crohn's disease or Ulcerative colitis Age ≥ 18 years old Disease in remission at least 2weeks by following criteria Crohn's disease: Crohn's Disease Activity Index(CDAI) < 150 Ulcerative colitis: Mayo Ulcerative Colitis Subscore ≤ 2 Prednisolone ≤ 15 mg/day for at least 1 month Stable immunomodulator dosage at least 1 month Stable biologic agent at least 2 months  Exclusion Criteria:  Patients with Ulcerative colitis with a history of proctocolectomy Patients with Crohn's disease with bowel stricture Patients with recently antibiotic usage within 1 month Pregnant patients