To effectively prevent deformation of an MEA and shift of GDLs, first GDLs, second GDLs, and separators are layered in order at both sides of the MEA in the thickness direction thereof, the gaskets which sandwich an end portion of the MEA outside the first GDLs and the second GDLs are made from rubber or a synthetic resin material having rubber-like elasticity and integrally provided on the separators respectively, the first GDLs have end portions which are formed so as to protrude beyond outer peripheries of the second GDLs, and the gaskets have support step portions which can position and support the end portions of the first GDLs at the same height as the support height by the second GDLs.