The present invention provides: a compound which can be applied to soil, stems or leaves and can exhibit a satisfactory herbicidal effect at a low dose； and an agrichemical composition, particularly a herbicide, which contains the compound. The present invention relates to: a pyridone derivative represented by general formula [1] [wherein R1 represents a C1-C6 alkyl group, a C2-C6 alkenyl group, a C1-C6 haloalkyl group or the like； R2 and R3 independently represent a hydrogen atom, a nitro group, a cyano group, a C1-C6 alkyl group or the like； and W represents a 5- or 6-membered cyclic group which may contain a nitrogen atom, an oxygen atom or a sulfur atom] or a salt thereof； and a herbicide containing the pyridone derivative or the salt thereof.
