A water electrolysis cell (100) includes an anode-side porous channel (10), a membrane electrode assembly (23), a cathode-side porous channel (30), and a separator (40) disposed on at least any one of a side of the anode-side porous channel (10) opposite to the membrane electrode assembly (23) side and a side of the cathode-side porous channel (30) opposite to the membrane electrode assembly (23) side. The anode-side porous channel (10), the membrane electrode assembly (23), and the cathode-side porous channel (30) are provided in this order. The membrane electrode assembly (23) includes an anode catalyst layer, an electrolyte membrane, and a cathode catalyst layer in order from the anode-side porous channel (10) side. An area in a plane direction of the anode-side porous channel (10) is greater than an area in the plane direction of the cathode-side porous channel (30) in a plan view.