A metal porous body mainly composed of nickel and having a framework of a three-dimensional network structure, Ni(OH) 2 being present in a surface of the framework, at least oxygen being invariably detected at any position within a depth of 5 nm from the surface, and hydrogen being detected at least in the surface, when the metal porous body is subjected to at least 30 potential scans between a lower limit potential of -0.10 V and an upper limit potential of +0.65 V with respect to a hydrogen standard potential in not less than 10% by mass and not more than 35% by mass of a potassium hydroxide aqueous solution, wherein the oxygen is detected by analyzing the surface in a depth direction of the framework using Auger electron spectroscopy (AES) according to the method described in the description and wherein the hydrogen is detected as water desorbed from the metal porous body at a temperature higher than an evaporation temperature of water adsorbed on the surface, by analyzing the surface using thermal desorption spectrometry (TDS) according to the method described in the description, the metal porous body having an average pore diameter of not less than 250 μm and not more than 500 μm, wherein the average pore diameter of the metal porous body is calculated as average pore diameter determined by dividing 25.4 mm by the number of cells, by observing the surface of the metal porous body with a microscope and counting the number of pores per 25.4 mm (inch) as the number of cells, Ni, NiO, Ni 2 O 3 , and Ni(OH) 2 are detected by analyzing the surface using X-ray photoelectron spectroscopy (XPS) according to the method described in the description, and a content of a total of Ni 2 O 3 and Ni(OH) 2 is higher than a content of NiO in the surface, the relative contents determined by comparing area sizes of the respective peaks when the surface of the framework of the metal porous body is analyzed using XPS according to the method described in the description. Ni(OH) 2 being present in a surface of the framework, at least oxygen being invariably detected at any position within a depth of 5 nm from the surface, and hydrogen being detected at least in the surface, when the metal porous body is subjected to at least 30 potential scans between a lower limit potential of -0.10 V and an upper limit potential of +0.65 V with respect to a hydrogen standard potential in not less than 10% by mass and not more than 35% by mass of a potassium hydroxide aqueous solution, wherein the oxygen is detected by analyzing the surface in a depth direction of the framework using Auger electron spectroscopy (AES) according to the method described in the description and wherein the hydrogen is detected as water desorbed from the metal porous body at a temperature higher than an evaporation temperature of water adsorbed on the surface, by analyzing the surface using thermal desorption spectrometry (TDS) according to the method described in the description, the metal porous body having an average pore diameter of not less than 250 μm and not more than 500 μm, wherein the average pore diameter of the metal porous body is calculated as average pore diameter determined by dividing 25.4 mm by the number of cells, by observing the surface of the metal porous body with a microscope and counting the number of pores per 25.4 mm (inch) as the number of cells, Ni, NiO, Ni 2 O 3 , and Ni(OH) 2 are detected by analyzing the surface using X-ray photoelectron spectroscopy (XPS) according to the method described in the description, and a content of a total of Ni 2 O 3 and Ni(OH) 2 is higher than a content of NiO in the surface, the relative contents determined by comparing area sizes of the respective peaks when the surface of the framework of the metal porous body is analyzed using XPS according to the method described in the description. <EOS>