It is to provide an electrolyte material with which an increase in the water content can be suppressed even when the ion exchange capacity of a polymer having repeating units based on a monomer having a dioxolane ring is high; and a membrane/electrode assembly excellent in the power generation characteristics under low or no humidity conditions and under high humidity conditions.It is to use an electrolyte material, which comprises a polymer (H) having ion exchange groups converted from precursor groups in a polymer (F), and having an ion exchange capacity of at least 1.35 meq/g dry resin, the polymer (F) having repeating units (A) based on a perfluoromonomer having a precursor group of an ion exchange group and a dioxolane ring and repeating units (B) based on a perfluoromonomer having no precursor group and having a dioxolane ring, and having a TQ of at least 200° C., which is a temperature at which the melt volume rate becomes 100 mm3/sec when the polymer (F) is subjected to melt-extrusion under an extrusion pressure condition of 2.94 MPa from a nozzle having a length of 1 mm and an inner diameter of 1 mm.