The present invention provides compounds useful as agents for the prevention or treatment of a disease associated with abnormal serum uric acid level and the like. That is, the present invention relates to indolizine derivatives represented by the following formula (I) having xanthine oxidase inhibitory activities and useful as agents for the prevention or treatment of a disease associated with abnormality of serum uric acid level, prodrugs thereof, salts thereof or the like. In the formula, ring U represents aryl or heteroaryl; R1 represents halogen, a hydroxy group or the like; R2 represents halogen, a hydroxy group, alkyl, alkoxy, alkyl substituted by fluorine, alkoxy substituted by fluorine or the like; m represents a number from 0 to 2; n represents a number from 0 to 3; and R3 represents hydrogen, fluorine or the like.