Production method for dihydropyrazinone derivative

Provided is a method for simple, high-yield production of a dihydropyrazinone derivative. The method is characterized by: continuously introducing, into a cylindrical reaction vessel, an epoxy compound indicated by formula (II), water, and at least one type of ethylene diamine selected from the group consisting of ethylene diamine, ethylene diamine acetic acid, and an ethylene diamine hydrate and reacting same in the cylindrical reaction vessel; and continuously obtaining a reaction product including a dihydropyrazinone derivative indicated by formula (I), from an outlet in the cylindrical reaction vessel. In the formulas, R1 indicates a C1-6 haloalkyl group and each X independently indicates a halogen atom. 提供简便且高收率的二氢吡嗪酮衍生物的制造方法。其特征在于，将式(II)的环氧化合物与选自由乙二胺、乙二胺酸盐和乙二胺水合物组成的组中的至少1种乙二胺类、及水连续地导入至管状反应器中，在管状反应器中使其反应，从该管状反应器的出口连续地得到包含式(I)的二氢吡嗪酮衍生物的反应产物。式中，R表示碳数1～6的卤代烷基，各X独立地表示卤素原子。