A water electrolysis device includes an electrolyte correction unit having a diaphragm, the device having an electrolyte correction unit, including a diaphragm, for removing a concentration difference inside an electrolyte, so as to prevent a gas composition in a gas phase area of the water electrolysis device from reaching an explosion limit and, simultaneously, prevent the occurrence of a difference in a liquid level due to a difference in the concentration of the electrolyte even if the electrolyte discharged from an anode chamber and the electrolyte discharged from a cathode chamber are each circulated independently, and thus does not require an additional device for solving same, and can resolve the problem of a reduction in processability according to electrolyte re-injection and operation stabilization.