NOVELTY - A cell has joined component (12) having fuel electrode and air electrode, gas diffusion component (I) which supplies fuel gas to fuel electrode, gas diffusion component (II) which supplies oxidizing gas to air electrode, separator, electric power generation portion (14a) in which joined component is positioned and manifold portion having a manifold opening portion (18) which is provided in circumference of electric power generation portion. The porosity of boundary portion of gas diffusion components is less than the porosity of power generation and manifold portion.    USE - Cell is used for fuel cell (claimed) such as polymer electrolyte fuel cell.    ADVANTAGE - The cell has excellent gas-seal property and reduced number of portions of unit cell. The fuel cell comprising the cell has excellent electric power generation efficiency.    DETAILED DESCRIPTION - A cell has joined component having fuel electrode and air electrode in electrolytic membrane, gas diffusion component (I) which supplies fuel gas to the fuel electrode, gas diffusion component (II) which supplies oxidizing agent gas to the air electrode, pair of separator which clamps the gas diffusion components and joined component, electric power generation portion in which the joined component is positioned and manifold portion having a manifold opening portion which is provided in the circumference of the electric power generation portion, and circulates fuel gas and oxidizing agent gas, to form coolant. The porosity of the boundary portion of gas diffusion components is less than the porosity of the power generation portion and manifold portion. At least one of the gas diffusion components is extended to the manifold portion and the peripheral portion is hermitically sealed by impregnating with liquid resin.    DESCRIPTION OF DRAWING(S) - The drawing shows the sectional view of the membrane electrode assembly in the cell. (Drawing includes non-English language text)    Membrane electrode assembly (10a)    Joined component (12)    Electric power generation portion (14a)    Gasket component (16)    Manifold opening portion (18)