MEMBRANE ELECTRODE ASSEMBLY AND FUEL CELL

A membrane electrode assembly includes an electrolyte membrane, and a pair of electrode layers which sandwich the electrolyte membrane. The pair of electrode layers include a pair of catalyst layers which sandwich the electrolyte membrane, and a pair of gas diffusion layers disposed on the pair of catalyst layers on opposite sides to the electrolyte membrane. At least one catalyst layer contains a fibrous electric conductor, catalyst particles, a particulate electric conductor, and a proton-conductive resin. The at least one catalyst layer has a first region at a distance of 200 nm or less from the fibrous electric conductor, and a second region at a distance of more than 200 nm from the fibrous electric conductor. Pores are present in the first and second regions. A mode diameter M1 of the pores in the first region and a mode diameter M2 of the pores in the second region satisfy M1