To provide a process for forming a catalyst layer whereby defects such as cracks are scarcely formed in the catalyst layer, and the bond strength is high at the interface between the catalyst layer and a reinforcing layer and at the interface between the catalyst layer and a polymer electrolyte membrane; and a process for producing a membrane/electrode assembly for a polymer electrolyte fuel cell, which is capable of exhibiting high power generation performance even under a low humidity condition and has sufficient mechanical strength and dimensional stability and which has excellent durability even in an environment where humidification and drying, etc. are repeated.
In the production of a membrane/electrode assembly 10, a first catalyst layer 22 (a second catalyst layer 34) is formed by a process comprising steps (a) and (b). (a) A step of applying a coating fluid comprising a catalyst and an ion-exchange resin, on a substrate to form a coating fluid layer. (b) A step of disposing a reinforcing layer 24 (34) on the coating fluid layer formed in the step (a) and then, drying the coating fluid layer to form a first catalyst layer 22 (a second catalyst layer 34).