The present invention provides compounds useful as agents for the prevention or treatment of a disease associated with abnormal plasma uric acid level and the like. The present invention relates to fused heterocyclic 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 plasma uric acid level, prodrugs thereof, salts thereof or the like. In the formula (I), T represents trifluoromethyl, nitro or cyano; ring Q represents heteroaryl; X1 and X2 independently represent CH or N; ring U represents aryl or heteroaryl; m represents integral number from 0 to 2; n represents integral number from 0 to 3; R1 represents a hydroxy group, amino or C1-6 alkyl; R2 represents C1-6 alkyl, C1-6 alkoxy C1-6 alkyl or the like.