Obj ect Provided is a catalyst having an excellent durability and being capable of lowering the cost of a fuel cell. Solving Means Disclosed is a catalyst configured to include a support and alloy particles including platinum and a metal component other than platinum supported on the support, wherein the catalyst includes mesopores having a radius of 1 to 10 nm originated from the support, wherein a mode radius of the mesopores is in a range of 2.5 to 10 nm, and wherein the alloy particles have a catalyst function, and at least a portion of the alloy particles is supported inside the mesopores.