Water electrolysis apparatus

A water electrolysis apparatus for producing hydrogen through electrolysis of water, the apparatus comprising:

• an electrolyte membrane;
• first and second current collectors disposed respectively on opposite sides of the electrolyte membrane;
• first and second separators stacked respectively on the current collectors;
• a first flow field defined by stacking the first current collector and the first separator;
• and
• a second flow field defined by stacking the second current collector and the second separator;
• and
• a passage communicating with at least the first flow field or the second flow field and which extends in a stacking direction of the first and second separators,
• wherein at least the first separator or the second separator has a seal groove annularly extending around the passage, a seal member being disposed in the seal groove, and
• a pressure-releasing chamber is disposed outwardly of the seal groove, is capable of communicating with the seal groove, and communicates with an outside through a depressurizing channel,
• wherein the electrolyte membrane extends through the pressure-releasing chamber, and
• the pressure-releasing chamber has a recess, the recess either facing the depressurizing channel across the electrolyte membrane or is formed in the electrolyte membrane.