An apparatus for measuring an amount of hydrogen generated due to corrosion of a specimen formed of a metallic material and penetrated into the metallic material by using an electrochemical hydrogen permeation method, the specimen having one surface exposed to a corrosive environment so as to serve as a penetration surface of hydrogen generated by a corrosion reaction while having the other surface as a hydrogen detection surface, the apparatus comprising: an electrochemical cell constituted of a group of a plurality of cells (7a, 7b, 7c, 7d) disposed on the hydrogen detection surface side, the cells (7a, 7b, 7c, 7d) in the cell group each being filled with an electrolyte aqueous solution having a pH of 9 to 13 and having a reference electrode and a counter electrode independently disposed therein, wherein at least one of the plurality of cells (7a, 7b, 7c, 7d) in the cell group is configured as a base cell for compensating a residual electric current, the base cell having a protective film formed on a region on the hydrogen penetration surface side corresponding to a hydrogen detection region thereof for the purpose of cutting off a contact with a corrosive environment, and wherein the apparatus is configured to compensate the anodic current values detected in other cells than the base cell based on the residual electric current value detected in the base cell, and to calculate an amount of hydrogen penetrating from a corrosive surface side based on the compensated anodic current values; the apparatus being characterized in that the electrolyte aqueous solution contains dimethylsulfoxide or dimethylformamide added thereto for the purpose of antifreezing and/or in that the electrochemical cell filled with the electrolyte aqueous solution has a gas body disposed therein, the gas body being arranged without coming into contact with the hydrogen detection surface. an electrochemical cell constituted of a group of a plurality of cells (7a, 7b, 7c, 7d) disposed on the hydrogen detection surface side, the cells (7a, 7b, 7c, 7d) in the cell group each being filled with an electrolyte aqueous solution having a pH of 9 to 13 and having a reference electrode and a counter electrode independently disposed therein, wherein at least one of the plurality of cells (7a, 7b, 7c, 7d) in the cell group is configured as a base cell for compensating a residual electric current, the base cell having a protective film formed on a region on the hydrogen penetration surface side corresponding to a hydrogen detection region thereof for the purpose of cutting off a contact with a corrosive environment, and wherein the apparatus is configured to compensate the anodic current values detected in other cells than the base cell based on the residual electric current value detected in the base cell, and to calculate an amount of hydrogen penetrating from a corrosive surface side based on the compensated anodic current values; the apparatus being characterized in that the electrolyte aqueous solution contains dimethylsulfoxide or dimethylformamide added thereto for the purpose of antifreezing and/or in that the electrochemical cell filled with the electrolyte aqueous solution has a gas body disposed therein, the gas body being arranged without coming into contact with the hydrogen detection surface.