A pyridone derivative, or a salt thereof, represented by formula (I), ** Formula ** wherein ring A represents an aryl, a heteroaryl or a group represented by the following formula (a), ** Formula ** (where Z1 and Z2 each independently represent -CH2- or -O-, and n1 indicates an integer from 1 to 3), R1 represents a hydrogen atom, a halogen atom, a hydroxyl group, a group cyano, a nitro group, a C1-C6 haloalkyl group, a carboxyl group, an optionally substituted C1-C6 alkyl group, an optionally substituted C1-C6 alkoxy group, an optionally substituted alkoxy (C1-C6) alkoxy group, a cycloalkyl group optionally substituted, an optionally substituted cyclohexylalkyl alkyl group, an optionally substituted heterocycloalkyl group, an optionally substituted heterocycloalkylalkyl group, an optionally substituted aryl group, an optionally substituted aralkyl group, an optionally substituted heteroaryl group, an optionally substituted heteroarylalkyl group, an optionally substituted C2-C6 alkenyl group, an optionally substituted alkenyl group, an optionally substituted cycloalkenyl group, an optionally substituted cycloalkenyl alkyl group, an optionally substituted heterocycloalkenyl group, an optionally substituted heterocycloalkenyl alkyl group Optionally substituted C6, or an optionally substituted alkylalkyl group, or -J1-X1-R5 {wherein J1 represents a single bond, alkylene, alkenylene or alkynylene, X1 represents a single bond, an oxygen atom, a sulfur atom, SO , SO2, - CO-, - NR6-, -NR6SO2-, -SO2NR6-, -NR6CO-, -CONR6-, -NR6COO-, -OCONR6-, -NR6CONR7-, or -NR6SO2NR7- (where R6 and R7 each independently represents a hydrogen atom or a C1-C6 alkyl group), R5 represents a hydrogen atom, a trifluoromethyl group, an optionally substituted C1-C6 alkyl group, a C alkoxy group Optionally substituted 1-C6, an optionally substituted cycloalkyl group, an optionally substituted cycloalkylalkyl group, an optionally substituted heterocycloalkyl group, an optionally substituted heterocycl
