The present invention provides an electrolyte membrane formed of an ion conductive composition. Said composition contains a liquid crystalline polymer having an ionic dissociative group. Molecular chains of the liquid crystalline polymer are orientated in a specific direction. The degree of orientation .alpha. of the liquid crystalline polymer is in a range of 0.45 or more and less than 1, as defined by equation (1) as follows, Degree of orientation .alpha.=(180-.DELTA..beta.)/180 (1), wherein .DELTA..beta. is a full width at half maximum of a peak in an X-ray diffraction intensity distribution pattern obtained by measuring an intensity distribution from 0 to 360 degrees in the azimuthal angle direction, at a peak scattering angle, in an X-ray diffraction image of the electrolyte membrane. Ionic conductivity in a thickness direction of the membrane is higher than the ionic conductivity in a direction parallel to a surface of the membrane. The present invention also provides a method for manufacturing an electrolyte membrane formed of an ion conductive composition.