In an manufacturing apparatus, a belt-shaped electrolyte polymer is conveyed in a state disposed to a back sheet. A first reinforcement membrane is conveyed in a state disposed to a back sheet, and, in a first sticking section, stuck with the belt-shaped electrolyte polymer. In a first thermocompression bonding section, the belt-shaped electrolyte polymer and the first reinforcement membrane are thermally compressed. At this time, a molten electrolyte polymer reaches between the first reinforcement membrane and the back sheet thereof, and the first adhesiveness between the first reinforcement membrane and the back sheet thereof becomes higher than the second adhesiveness between the belt-shaped electrolyte polymer and the back sheet thereof. A first peel section peels, in this state, the back sheet from the belt-shaped electrolyte polymer.