An electrolyte film, characterized in that it comprises inorganic proton electroconductive oxide particles and a matrix component selected from an organic resin and an inorganic matrix component. The inorganic proton electroconductive oxide particles preferably comprises hydrated antimony oxide particles which is represented by the following formula (1): Sb<sb>2</sb>O<sb>5</sb> · nH<sb>2</sb>O (1) wherein n = 0.1 to 5, and have an average particle diameter in the range of 5 to 50 nm and the hydrated antimony oxide particles are preferably contained in the electrolyte film in a content of 5 to 80 wt % in terms of the oxide (Sb<sb>2</sb>O<sb>5</sb>). The electrolyte film can be used for manufacturing a fuel cell exhibiting high cell performance even in a long term operation or a high temperature operation.
