PURPOSE: To inexpensively prepare the title electrode in good yield by constituting a liquid communication part of a porous polyvinyl chloride film formed by removing a plasticizer from a mixed film of polyvinyl chloride and the plasticizer.

CONSTITUTION: In a comparison electrode having an internal liquid stored therein and equipped with an internal electrode and a liquid communication part, the liquid communication pat is constituted of a porous polyvinyl chloride film formed by removing a plasticizer from a mixed film of polyvinyl chloride and the plasticizer. As polyvinyl chloride, usual polyvnyl chloride or a vinyl chloride polymer having film forming properties can be used and other monomer (e.g., vinylidene chloride) may be partially contained as a constitutional unit. The plasticizer means the plasticizer of polyvinyl chloride and various org. acid esters, for example, phthalic esters (dibutyl phthalate), adipic esters (dibutyl adipate) or sebacic ester (di-2-ethylhexyl sebacate) are pref. designated. As a solvent, a usual polar org. solvent capable of dissolving both of polyvinyl chloride and the plasticizer, for example, tetrahydrofuran is designated.