Electrolyte material, and proton conductive polymer electrolyte membrane, membrane electrode assembly and polymer electrolyte fuel cell using the same

Disclosed is an electrolyte material containing a copolymer including a polyvinyl as a main chain, the copolymer including a functional group with proton conductivity; and an alkoxide of Si or Ti as a side chain. By using the electrolyte material, a proton conductive polymer electrolyte membrane with flexibility, high ion conductivity, excellent water resistance, and a small change in size can be obtained. And a polymer electrolyte fuel cell can be provided which has high output and durability by using the electrolyte membrane.