The present invention provides an electrolyte having high conductivity even under high-temperature low-humidification conditions (e.g. at a temperature of 100 to 120° C. and a humidity of 20 to 50% RH) and thereby makes it possible to realize a higher performance fuel cell. The present invention is a fluoropolymer electrolyte having an equivalent weight (EW) of not less than 250 but not more than 700 and a proton conductivity of not lower than 0.10 S/cm as measured at a temperature of 110° C. and a relative humidity of 50% RH and comprising a COOZ group- or SO3Z group-containing monomer unit, wherein Z represents an alkali metal, an alkaline earth metal, hydrogen atom or NR1R2R3R4 in which R1, R2, R3 and R4 each independently represents an alkyl group containing 1 to 3 carbon atoms or hydrogen atom.