A photoelectrode structure, comprising: an electrode; a light absorbing layer; a composite protective layer on the light absorbing layer; and an electrocatalyst on the composite protective layer, wherein the composite protective layer comprises: a chemical protective layer, wherein the chemical protective layer comprises at least one metal selected from tantalum, niobium, and titanium, and an alloy thereof; and a physical protective layer different from the chemical protective layer, wherein the physical protective layer has a thickness of 1-100 μm and comprises at least one selected from: at least one metal selected from aluminum, copper, tantalum, niobium, and titanium, an alloy thereof, and stainless steel, at least one carbon material selected from amorphous carbon, graphite, and graphene, at least one an oxide conductor selected from In 2 O 3:Sn, SnO 2:F, ZnO:Al, TiO 2:Nb, and SrTiO 3:Nb, and an inorganic material-polymer composite conductor; wherein the chemical protective layer has a thickness of 1/100 th to 1/10 th of the thickness of the physical protective layer, and has a corrosion rate of 0.1 Coulombs per square centimeter per 10 hours or less when evaluated at a water decomposition potential, and the physical protective layer has moisture transmittance rate of 0.001 grams per square meter per day or less and has an electrical conductivity. an electrode; a light absorbing layer; a composite protective layer on the light absorbing layer; and an electrocatalyst on the composite protective layer, wherein the composite protective layer comprises: a chemical protective layer, wherein the chemical protective layer comprises at least one metal selected from tantalum, niobium, and titanium, and an alloy thereof; and a physical protective layer different from the chemical protective layer, wherein the physical protective layer has a thickness of 1-100 μm and comprises at least one selected from: at least one metal selected from aluminum, copper, tantalum, niobium, and titanium, an alloy thereof, and stainless steel, at least one carbon material selected from amorphous carbon, graphite, and graphene, at least one an oxide conductor selected from In 2 O 3:Sn, SnO 2:F, ZnO:Al, TiO 2:Nb, and SrTiO 3:Nb, and an inorganic material-polymer composite conductor; wherein the chemical protective layer has a thickness of 1/100 th to 1/10 th of the thickness of the physical protective layer, and has a corrosion rate of 0.1 Coulombs per square centimeter per 10 hours or less when evaluated at a water decomposition potential, and the physical protective layer has moisture transmittance rate of 0.001 grams per square meter per day or less and has an electrical conductivity. a chemical protective layer, wherein the chemical protective layer comprises at least one metal selected from tantalum, niobium, and titanium, and an alloy thereof; and a physical protective layer different from the chemical protective layer, wherein the physical protective layer has a thickness of 1-100 μm and comprises at least one selected from: at least one metal selected from aluminum, copper, tantalum, niobium, and titanium, an alloy thereof, and stainless steel, at least one carbon material selected from amorphous carbon, graphite, and graphene, at least one an oxide conductor selected from In 2 O 3:Sn, SnO 2:F, ZnO:Al, TiO 2:Nb, and SrTiO 3:Nb, and an inorganic material-polymer composite conductor; wherein the chemical protective layer has a thickness of 1/100 th to 1/10 th of the thickness of the physical protective layer, and has a corrosion rate of 0.1 Coulombs per square centimeter per 10 hours or less when evaluated at a water decomposition potential, and the physical protective layer has moisture transmittance rate of 0.001 grams per square meter per day or less and has an electrical conductivity. at least one metal selected from aluminum, copper, tantalum, niobium, and titanium, an alloy thereof, and stainless steel, at least one carbon material selected from amorphous carbon, graphite, and graphene, at least one an oxide conductor selected from In 2 O 3:Sn, SnO 2:F, ZnO:Al, TiO 2:Nb, and SrTiO 3:Nb, and an inorganic material-polymer composite conductor; wherein the chemical protective layer has a thickness of 1/100 th to 1/10 th of the thickness of the physical protective layer, and has a corrosion rate of 0.1 Coulombs per square centimeter per 10 hours or less when evaluated at a water decomposition potential, and the physical protective layer has moisture transmittance rate of 0.001 grams per square meter per day or less and has an electrical conductivity.