The present invention provides: a compound represented by formula (I) or a pharmaceutically acceptable salt thereof, which has an excellent inhibitory activity on xanthine oxidase and is useful as a therapeutic agent or a prophylactic agent for diseases associated with xanthine oxidase, such as gout, hyperuricemia, tumor lysis syndrome, urinary tract stone, hypertension, dyslipidemia, diabetes, cardiovascular diseases including arteriosclerosis and heart failure, renal diseases including diabetic nephropathy, respiratory diseases including chronic obstructive pulmonary disease, inflammatory bowel disease or autoimmune diseases； and a medicine or a pharmaceutical composition comprising the compound or the salt as an active ingredient.
