Abstract: The present application relates to a method for manufacturing a photoelectrode, the method comprising steps of impregnating a first transition metal oxide capable of performing photoreaction in an electrolyte, applying a voltage onto the electrolyte to generate an electrochemical oxidation reaction on the surface of the first transition metal oxide, and forming a second transition metal oxide thin film on the surface of the first transition metal oxide by irradiating light onto the first transition metal oxide at the same time as the step of applying the voltage.