The utility model relates to a comprehensive treatment device of a water electrolysis hydrogen production device and belongs to the technical field of electrolytic water of hydrogen or oxygen. A gas inlet is formed at the bottom of a tank body of the device, and an outlet of a water supplementing overflow pipe extends to the bottom of a gas-liquid separator; a water supplementing inlet communicated with outside is formed at the lower part of the tank body; a reflux component is arranged at the middle part of the tank body; and a drop capture mesh is arranged at the upper part of the tank body. The comprehensive treatment device of the water electrolysis hydrogen production device performs integration and supplementation against the prior art, centralizes multiple steps in the process of producing hydrogen by water electrolysis and further proposes a comprehensive treatment device which simultaneously performs washing, cooling and water supplementation on a system in the process of producing hydrogen by water electrolysis, thereby realizing integration of multiple functions, reducing total occupied area of the water electrolysis hydrogen production device, saving cost and improving the integral space utilization rate of the device.