PURPOSE: To obtain an ionic conductor having small humidity dependence and stable ionic conductivity by blending an ionic conductor comprising a perfluorosulfonic acid polymer, etc., as a matrix with an organic compound of a hydrophilic anionic type.

CONSTITUTION: (A) in ionic conductor comprising a perfluorosulfonic acid polymer and/or perfluorosulfonate polymer as a matrix is blended with (B) 0.1W30wt.% organic compound of a hydrophilic anionic type (e.g., one containing a proton as pair ion when the compound A is protonic conductor) to give the aimed ionic conductor suppressing variability of water content of ionic conductor resulting from relative humidity of the circumference and capable of controlling reduction in ionic conductivity in a dried atmosphere.