To provide a catalyst that has superior durability while achieving a reduction in cost of the fuel cell. The catalyst comprises a carrier and alloy microparticles carried by the carrier and containing platinum and a metal component other than platinum, wherein the catalyst has mesopores having a radius of 1-10 nm derived from the carrier, the mode radius of the mesopores is 2.5-10 nm, the alloy microparticles have a catalytic effect, and at least a portion of the alloy microparticles are carried within the mesopores.