The present invention provides compounds useful as agents for the prevention or treatment of a disease associated with abnormal serum uric acid level which has a uricosuric activity or the like. The present invention relates to (aza)indole derivatives represented by the following general 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, or salts thereof. In the formula (I), T represents nitro or cyano and the like; ring J represents aryl or heteroaryl and the like; Q represents carboxy or 5-tetazolyl and the like; Y represents H, OH, NH2, halogen, nitro, alkyl, alkoxy and the like; X1, X2 and X3 independently represent CR2 or N; R1 and R2 independently represent halogen, cyano, haloalkyl, A-D-E-G, —N(-D-E-G)2 and the like, in the formula, A represents a single bond, O, S and the like; D and G independently represent optionally substituted alkylene, cycloalkylene, heterocycloalkylene, arylene, heteroarylene and the like; E represents a single bond, O, S, COO, SO2 and the like.