When manufacturing an electrode for an electrolytic capacitor, in a first hydration step (ST1), an aluminum electrode is immersed in a first hydration processing solution having a temperature of at least 70° C. and comprising pure water or an aqueous solution to which phosphoric acid or a phosphate has been added so that the phosphorus concentration is no greater than 4 mass ppm. In a second hydration step (ST2), the aluminum electrode is immersed in a second hydration processing solution to which phosphoric acid or a phosphate has been added so that the phosphorus concentration is 4-5000 mass ppm, the second hydration processing solution having a pH of 3.0-9.0 and a temperature of at least 70° C. In a chemical conversion step (ST3), at least a boric acid chemical conversion process in which the aluminum electrode is chemically converted in a boric acid-based chemical conversion solution is included, and a chemical conversion coating having a coating withstand voltage of at least 200 V is formed on the aluminum electrode.