A process for producing a 2,3-dihydropyridazine compound represented by the formula (2): wherein R1, R2 and R3 are the same or different and each represents a hydrogen atom, a halogen atom, an alkyl group which may be substituted with a halogen atom or atoms, an alkenyl group which may be substituted with a halogen atom or atoms, an alkoxy group which may be substituted with a halogen atom or atoms, an alkylthio group, an alkylsulfenyl group, an alkylsulfonyl group or a dialkylamino group; which comprises reacting a salt consisting of bromoacetic acid and an amine compound with a pyridazine compound represented by the formula (1): wherein R1, R2 and R3 are the same meanings as defined above.