A cathode of a battery including an electrolyte membrane, containing a first layer which contains 0.3 mg/cm2 or more and 9.0 mg/cm2 or less of a carbon catalyst; and a second layer which is arranged between the electrolyte membrane and the first layer in the battery, and which contains 0.002 mg/cm2 or more and 0.190 mg/cm2 or less of platinum. The carbon catalyst has a ratio of a mesopore volume to a total pore volume of 30% or more.