TECHNOLOGY FOCUS - INSTRUMENTATION AND TESTING - Preferred Components: The anode diffusion layer and the cathode diffusion layer is set out in such a way, not to totally overlap the anode or cathode catalyst layer with which it comes into contact. The anode diffusion layer protrudes beyond the anode catalyst layer by 100-300 microns, inclusive. The anode diffusion layer end/cathode diffusion layer end is apart from the anode catalyst layer end by 100-300 um, inclusive. The cathode diffusion layer protrudes beyond the cathode catalyst layer by 100-300 microns, inclusive. The anode diffusion layer and the cathode diffusion layer is smaller than the respective anode catalyst layer and cathode catalyst layer to be set out inside of the respective anode catalyst layer and cathode catalyst layer. The anode diffusion layer and the cathode diffusion layer are larger than the respective anode catalyst layer and cathode catalyst layer to protrude beyond the respective anode catalyst layer and cathode catalyst layer. The cathode diffusion layer/anode diffusion layer is laid on the cathode catalyst layer of rectangular shape and essentially the same size, and has the corners cut off, to be out of alignment with the cathode catalyst layer by the cut off corners and partly expose the cathode catalyst layer/anode catalyst layer. (A) comprises: an adhesive layer for protecting the catalyst layer is provided between the protruded portion and electrolyte membrane; a gasket for tightly sealing a gas supplied as a fuel or oxidant to the membrane electrode assembly, at least one of the anode diffusion layer and the cathode diffusion layer being out of alignment, at least at one end, with the cathode catalyst layer or anode catalyst layer end, and the end of the catalyst layer for the membrane electrode assembly is positioned on the outer side of the outer periphery of the gasket. The adhesive layer for protecting the catalyst layer is made of a material having the same composition as a binder used for producing the membrane electrode assembly, epoxy resin, hydrocarbon- based resin, silicone-based resin or UV-curable resin.