An electrolyzer is comprised of an anode and a cathode which are in contact with an electrolytic solution, wherein at least one of the anode and the cathode is composed of an electric conductor having a gas permeable structure comprising a gas generating surface at which gas is generated by electrolysis of the electrolytic solution, a plurality of through holes leading from the gas generating surface to a different surface and allowing the gas generated on the gas generating surface to selectively pass therethrough, and a gas releasing surface which is the different surface for releasing the gas supplied from the gas generating surface via the through holes. At least one of a surface treatment which causes the gas generating surface to be lyophilic for the electrolytic solution and a surface treatment which causes the gas releasing surface to be lyophobic for the electrolytic solution is performed.