A method of producing an MEA includes a first joining step of joining an anode to one surface of a solid polymer electrolyte membrane to thereby form a joint body and a second joining step of joining a cathode to another surface of the solid polymer electrolyte membrane. In the first joining step, the solid polymer electrolyte membrane is attracted by suction and heated through the anode placed on a suction/heating surface of a suction/heating plate. In the second joining step, a stack body of the joint body and the cathode is pressed and heated in a stacking direction, between the suction/heating surface and a heating plate.