In order to prevent decrease of power generation due to a narrow MEA reaction region, an MEA (2) arranged between a pair of separators (5), a rubber sheet (6) arranged on its planar extension at the outer circumferential side of the MEA (2), and a gasket-like lip line (7) formed at the opposite sides of the rubber sheet (6) integrally therewith to closely contact with the separators (5) are provided, a rubber impregnated portion (8) for integrating the rubber sheet (6) with the MEA (2) by impregnation of a part of rubber composing the rubber sheet (6) into the GDL (4) constituting the MEA (2) is provided at the circumferential edge of the MEA (2), and a GDL constricted portion (9) for regulating the rubber impregnated portion is provided at the immediately inner circumferential side of the rubber impregnated portion (8) in the plane of the MEA (2).