The present invention is to provide an oxopyrazine derivative having an excellent herbicidal activity and besides exhibiting high safety for useful crops and the like, or a salt thereof, and a herbicide containing the same.The present invention relates to an oxopyrazine derivative represented by formula [I]: wherein X1 represents an oxygen atom or a sulfur atom; X2 represents CH or N(O)m; m represents an integer of 0 or 1; R1 represents a hydrogen atom, a C1-C12 alkyl group and the like; R2 represents a halogen atom, a cyano group and the like; R3 is a hydroxyl group, a halogen atom and the like; A1 represents C(R4R5); A2 represents C(R6R7) or C═O; A3 represents C(R8R9); R4 to R9 represent a hydrogen atom or an alkyl group, or a salt thereof, and a herbicide containing these compounds.