Disclosed is a compound useful as a prophylactic or therapeutic agent for diseases associated with abnormal plasma uric acid levels and the like. Specifically disclosed are: a phenylisonicotinic acid derivative represented by formula (I), a prodrug thereof, or a salt thereof, which has a xanthine oxidase inhibiting activity and an URAT1 inhibiting activity and is useful as a prophylactic or therapeutic agent for diseases associated with abnormal plasma uric acid levels； and others. In formula (I), R1 represents a cyano, a trifluoromethyl, or the like； R2 represents H, a fluorine, or the like； and R3 represents W, or a group represented by formula -X-Y-Z (wherein W represents H, a halogen, a hydroxy group, a cycloalkyl, a heterocycloalkyl, or the like； X represents a single bond, -NH-, -O-, or the like； Y represents an alkylene, or the like； Z represents H, a haloalkyl, a hydroxy group, an alkoxy, a cycloalkyl, a heterocycloalkyl, an aryl, or the like).
