NOVELTY - Forming solid electrolyte multilayer membrane involves casting two dopes onto running support to form casting membrane (112) with two layers (112a, 112b) of the dopes respectively, where first dope (114) contain organic solvent and solid electrolyte that is fuel cell electrolyte layer, and second dope (115) contain the electrolyte, solvent and catalyst promoting redox reaction of electrodes in fuel cell; peeling the membrane as wet membrane from support; and drying in a state that both side edges are held by holding devices, and then second drying of membrane supported by rollers.    USE - For production of solid electrolyte multilayer membrane useful in membrane electrode assembly that is used in fuel cell (claimed). The assembly and the fuel cell are applicable to power sources for various mobile appliances and various portable appliances.    ADVANTAGE - The membrane has excellent proton conductivity for a fuel cell. The method provides the membrane with catalyst layers that promote the redox reaction at a low cost; and has uniform quality. The fuel cell comprising the membrane, realizes an excellent electromotive force.    DETAILED DESCRIPTION - Production of solid electrolyte multilayer membrane involves casting first dope and second dope onto running support to form casting membrane (112) having first layer (112a) of the first dope (114) and second layer (112b) of the second dope (115), where the first dope contain an organic solvent and a solid electrolyte that is solid electrolyte layer of fuel cell, and the second dope contain the solid electrolyte, the solvent and catalyst promoting redox reaction of electrodes in the fuel cell; peeling the casting membrane as wet membrane from the support; performing first drying of the wet membrane in a state that both side edges are held by holding devices; and performing second drying of the wet membrane supported by rollers. INDEPENDENT CLAIMS are included for the following:    (1) an apparatus of producing the solid electrolyte multilayer membrane comprising a casting device (111) for casting several dopes from a casting die (89) onto a running support to form a layered casting membrane and peeling the casting membrane as a layered wet membrane; a first drying device for drying the wet membrane in a state that both side edges are held by holding devices; and a second drying device for drying the wet membrane supported by rollers to form the solid electrolyte multilayer membrane, where the second drying device is disposed at a downstream of the first drying device, the several dopes are the first and the second dopes;    (2) a membrane electrode assembly comprising the solid electrolyte multilayer membrane; an anode adhered to one surface of the multilayer membrane, where the anode generating protons from a hydrogen-containing material supplied from outside; and a cathode adhered to the other surface of the multilayer membrane, where the cathode synthesizing water from the protons permeated through the multilayer membrane and gas supplied from outside; and    (3) a fuel cell comprising the membrane electrode assembly; and current collectors one of which provided in contact with the anode and the other is provided in contact with the cathode. The current collector on the anode side receives and passes electrons between the anode and outside; and the current collector on the cathode side receives and passes the electrons between the cathode and outside.    DESCRIPTION OF DRAWING(S) - The figure illustrates a sectional view of co-casting device.    belt (82)    casting die (89)    simultaneous co-casting device (111)    casting membrane (112)    first surface layer (112a)    second surface layer (112b)    third surface layer (112c)    first dope (114)    second dope (115)    third dope (116)    dop feeding passages (L1, L2, L3)    feed block. (119)