Provided are: an isoxazolin-5-one derivative represented by general formula (1); and a herbicide which contains the isoxazolin-5-one derivative as an active ingredient. In general formula (1), R1 represents a C1-C6 haloalkyl group; R2-R4 and X represent specific substituents or the like, respectively; n represents an integer of 1-4; and in cases where n represents an integer of 2-4, the X moieties may be different from each other.