Provided are a membrane electrode assembly having a structure in which a cathode catalyst layer, a hydroxide ion-conductive membrane, and an anode catalyst layer are laminated in this order, in which a tensile strength (a) and a breaking elongation (b) of a water-swollen body of a polymer contained in the cathode catalyst layer and/or the anode catalyst layer and a tensile strength (c) and a breaking elongation (d) of a water-swollen body of a hydroxide ion-conductive polymer constituting the hydroxide ion-conductive membrane satisfy the following relationships (Ri) and (Rii), a method for producing hydrogen, and a hydrogen production system. Tensile ⁢ strength ⁢ ( a ) > tensile ⁢ strength ⁢ ( c ) ( Ri ) Breaking ⁢ elongation ⁢ ( b ) > breaking ⁢ elongation ⁢ ( d ) ( Rii )