The present invention provides a process for producing a hydrazone compound represented by the general formula (5): which comprises a step of condensing a hydrazine compound represented by the general formula (3): with a carbonyl compound represented by the general formula (4): without taking the hydrazine compound out of a reactor. According to the invention, the target hydrazone compound can be obtained in high quality and in a high yield without taking the hydrazine compound out of the reactor at all, the hydrazine compound being a reaction intermediate which is structurally unstable and has a fear of influencing safety of workers owing to its toxicity (mutagenicity).