The present invention relates to a composition or a method for treating or preventing irritable bowel syndrome. The present invention uses Atractylodes japonica rhizome extract, preferably the ethanol water solution extract of Atractylodes japonica rhizome, more preferably the 35-65 v/v% ethanol water solution extract of Atractylodes japonica rhizome for treating or preventing irritable bowel syndrome. Atractylodes japonica rhizome extract shows a surprising effect in suppressing visceral hypersensitivity or improving defecation abnormality caused by stress or bowel irritability.