In electrochemical reaction generally involving gas decomposition, capable of advancing the electrochemical reaction at a high efficiency while preventing increase in pressure loss, to provide an electrochemical reaction element. Method for producing an electrochemical reaction device of the present invention, the fuel electrode 2 of the porous, to produce an electrochemical reaction device comprising a MEA7 consisting cathode 5 of the solid electrolyte 1 and the porous, fuel electrode 2 or the air electrode 5 above, by a vapor phase method, group III atoms, characterized in that it comprises a step of forming a solid electrolyte 1 comprising a doped barium zirconate.