A catalyst layer, includes: a carrier; metal particles located over the carrier; an underlayer located on the carrier; and an ionomer-based layer located over the underlayer, wherein the underlayer includes a polymer material, and covers at least parts of the metal particles, and the ionomer-based layer includes a proton-conducting resin. A fuel cell electrode includes the catalyst layer, and a fuel cell including the above catalyst layer. A method for producing a catalyst layer, includes: bringing at least one first solution including a polymer material into contact with a metal-particle-supported carrier to form an underlayer; and bringing a second solution including a proton-conducting resin into contact with the metal-particle-supported carrier to coat said metal-particle-supported carrier with the proton-conducting resin.