Abstract: A fuel cell membrane-electrode assembly having a fuel electrode and an oxidant electrode has a non-supported-catalyst containing catalyst layer that contains a metal catalyst nanoparticle of 0.3 nm to 100 nm in primary particle diameter that is not supported on a support, and an electrochemically active surface area of the metal catalyst nanoparticle is 10 m2/g to 150 m2/g, and a layer thickness of the non-supported-catalyst containing catalyst layer is less than or equal to 10 ?m.