A solid polymer fuel cell includes an electrolyte membrane having a polymer ion-exchange component, and an air electrode and a fuel electrode between which the electrolyte membrane is sandwiched. Each of the air electrode and the fuel electrode can be formed of a polymer ion-exchange component and a plurality of catalyst particles including a catalyst metal carried on surfaces of carbon black particles, and includes no third component. When a moistening for maintaining the electrolyte membrane in a wet state is carried out from both of the side of the air electrode and the side of the fuel electrode, the carbon black particles have a water-repellent property such that an amount A of water adsorbed under a saturated steam pressure at 60 C. is equal to or smaller than 80 cc/g, and a ratio Wp/Wc of a weight Wp of polymer ion-exchange component incorporated to a weight Wc of carbon black particles incorporated is set in a range of 0.4Wp/Wc1.25.