The present invention provides an herbicide composition with which it is possible to effectively control growth of undesirable plants among useful plants, the herbicide composition being very safe with respect to useful plants and exhibiting great effect at low dosages. This herbicide composition is characterized by containing, as active ingredients, [component A] selected from the group consisting of oxopyrazine derivatives represented by formula [X] (where R represents a C1-6 lower alkyl group and X represents a halogen atom) and salts thereof, and [component B] described in the specification.
