A cathode catalyst layer of fuel cells, the cathode catalyst layer including a first fibrous electrically-conductive member, a first particulate electrically-conductive member, first catalyst particles, and a first proton conductive resin. A ratio I1/C1 of a mass of the first proton conductive resin to a mass of the first electrically particulate conductive member is in a range of 1.0 to 1.6. A ratio of the first fibrous electrically-conductive member to 100 parts by mass of the first particulate conductive member is 30 to 50 parts by mass. The first proton conductive resin has an EW value of 600 to 850.