A fuel-cell unit cell comprising: an electrode stack having (a) a membrane-electrode assembly in which electrode catalyst layers (21q, 21r) are respectively laid on both surfaces of an electrolyte layer, (b) a first gas diffusion layer laid on a first surface of the membrane-electrode assembly except for an outer peripheral edge portion of the membrane-electrode assembly, and (c) a second gas diffusion layer laid on a second surface of the membrane-electrode assembly; a support frame disposed so as to surround the first gas diffusion layer; a first separator that is laid on a side of the electrode stack on which the first gas diffusion layer is located, in contact with the first gas diffusion layer, and that is fixed to the support frame; and a second separator that is laid on a side of the electrode stack on which the second gas diffusion layer is located, in contact with the second gas diffusion layer, and that is fixed to the support frame, wherein, at a first part of the fuel-cell unit cell: the fuel-cell unit cell has a bonding layer; between the first separator and an outer peripheral edge portion of the first gas diffusion layer, the bonding layer bonds the first separator and the outer peripheral edge portion together; between the first separator and the outer peripheral edge portion of the membrane-electrode assembly, the bonding layer is bonded to the outer peripheral edge portion of the membrane-electrode assembly; and between the first separator and the support frame, the bonding layer bonds the support frame and the first separator together; characterized in that, at a second part of the fuel-cell unit cell: the first separator has a reactant gas flow passage; a cover plate extends from between the first separator and the outer peripheral edge portion of the first gas diffusion layer to between the first separator and the support frame through between the first separator and the outer peripheral edge portion of the membrane-electrode assembly; between the cover plate and the outer peripheral edge portion of the first gas diffusion layer, the bonding layer bonds the cover plate and the outer peripheral edge portion of the first gas diffusion layer together; between the first separator and the outer peripheral edge portion of the membrane-electrode assembly, the bonding layer is bonded to the outer peripheral edge portion of the membrane-electrode assembly; between the cover plate and the support frame, the bonding layer bonds the cover plate and the support frame together; and the bonding layer is thus separated from the reactant gas flow passage of the first separator. an electrode stack having (a) a membrane-electrode assembly in which electrode catalyst layers (21q, 21r) are respectively laid on both surfaces of an electrolyte layer, (b) a first gas diffusion layer laid on a first surface of the membrane-electrode assembly except for an outer peripheral edge portion of the membrane-electrode assembly, and (c) a second gas diffusion layer laid on a second surface of the membrane-electrode assembly; (a) a membrane-electrode assembly in which electrode catalyst layers (21q, 21r) are respectively laid on both surfaces of an electrolyte layer, (b) a first gas diffusion layer laid on a first surface of the membrane-electrode assembly except for an outer peripheral edge portion of the membrane-electrode assembly, and (c) a second gas diffusion layer laid on a second surface of the membrane-electrode assembly; a support frame disposed so as to surround the first gas diffusion layer; a first separator that is laid on a side of the electrode stack on which the first gas diffusion layer is located, in contact with the first gas diffusion layer, and that is fixed to the support frame; and a second separator that is laid on a side of the electrode stack on which the second gas diffusion layer is located, in contact with the second gas diffusion layer, and that is fixed to the support frame, the fuel-cell unit cell has a bonding layer; between the first separator and an outer peripheral edge portion of the first gas diffusion layer, the bonding layer bonds the first separator and the outer peripheral edge portion together; between the first separator and the outer peripheral edge portion of the membrane-electrode assembly, the bonding layer is bonded to the outer peripheral edge portion of the membrane-electrode assembly; and between the first separator and the support frame, the bonding layer bonds the support frame and the first separator together; characterized in that, at a second part of the fuel-cell unit cell: the first separator has a reactant gas flow passage; a cover plate extends from between the first separator and the outer peripheral edge portion of the first gas diffusion layer to between the first separator and the support frame through between the first separator and the outer peripheral edge portion of the membrane-electrode assembly; between the cover plate and the outer peripheral edge portion of the first gas diffusion layer, the bonding layer bonds the cover plate and the outer peripheral edge portion of the first gas diffusion layer together; between the first separator and the outer peripheral edge portion of the membrane-electrode assembly, the bonding layer is bonded to the outer peripheral edge portion of the membrane-electrode assembly; between the cover plate and the support frame, the bonding layer bonds the cover plate and the support frame together; and the bonding layer is thus separated from the reactant gas flow passage of the first separator.