To provide an apparatus for producing water which contains free chlorine and is set at a pH value freely in a wide range from acidity to alkalinity.

This water electrolysis apparatus is partitioned to electrolytic chambers 15, 16 for electrolyzing raw water and an electrolyte housing chamber 17 for housing an aq. electrolyte soln. by two sets of electrode plate A, B and is arranged with an electrode C in this electrolyte housing chamber 17. Two sets of the electrode plate A, B of this water electrolysis apparatus are respectively the electrode plates formed by laminating sheet-like electrodes having many holes and sheet-like diaphragms and the respective electrode plates are so arranged that the diaphragm surfaces exist on the electrolyte housing chamber 17 side and the electrode surfaces exist on the electrolytic chamber 15, 16 side. The electrode C may be omitted. The one-side sheet-like diaphragms of the electrode plate A, B are preferably formed as anion exchange membranes and the other sheet-like diaphragms as cation exchange membranes. Nonconductive materials having many pores may be interposed between the sheet-like electrodes and sheet-like diaphragms of the electrode plates A, B.