PURPOSE: To provide a water redox potential control device capable of affording water of which the redox potential is changed to a desired value without using chemicals and simple in handling, maintenance and control.

CONSTITUTION: Air or oxygen is injected into the water 11 charged in a water tank 10 by an air amt. control device and, at the same time, a sonic wave is applied to the water 11 by a sonic wave generator 2 and a sonic wave generation amt. control device 3. Whereupon, the redox potential of the water 11 is changed and the change value is detected by the redox potensial sensor arranged in the vicinity of the bottom part of the water tank 10 to be inputted to a redox potential indicating controller 5. As a result, the injection amt. of air or oxygen and the irradiation quantity of a sonic wave are respectively adjusted are controlled to proper values with respect to the air amt. control device 1 and the sonic wave generation amt. control device 3 to obtain water having desired redox potential.