TECHNOLOGY FOCUS - INORGANIC CHEMISTRY - Preferred Components: The transition metal is at least one metal comprising titanium, vanadium, chromium, manganese, iron, cobalt, nickel, copper or zinc. The precious metal is at least one metal comprising iridium, gold, platinum, rhodium or silver. The catalyst particle has a surface or an outermost atomic layer that does not comprise an atom of the transition metal. The electrode catalyst further comprises a carbon-based support. The first catalyst further comprises a carbon-based support. The first catalyst particle further comprises atoms of a precious metal having a higher standard reduction potential than the transition metal. The amount of the precious metal in the precious metal precursor is 0.5-20 parts by weight based on 100 parts by weight of the first catalyst. The second mixture further comprises at least one of a glycol-based solvent and an alcohol-based solvent. In the method, when X1 and Y1 respectively denote amounts of a transition metal and a precious metal in an inductively coupled plasma (ICP) measurement of the first catalyst in the amount of A g, and X2 and Y2 respectively denote amounts of the transition metal and the precious metal of an ICP measurement of the electrode catalyst in the amount of A+B g, X1 greater than X2 and Y1 less than Y2, where B denotes the amount of the precious metal in the precious metal precursor, and conditions for the ICP analysis are a radio frequency (RF) source of 27.12 MHz and a sample uptake rate of 0.8 ml/minute. The difference between a diffraction angle (2theta) of a (111) peak of an X-ray diffraction pattern of the first catalyst measured by Ka1 of copper, and a diffraction angle (2theta) of a (111) peak of an X-ray diffraction pattern of the electrode catalyst measured by Ka1 of copper is less than or equal to 0.1. The cathode comprises the electrode catalyst. Preferred Method: In the converting of the first catalyst, atoms of the transition metal existing on the surface of the first catalyst particle are substituted by atoms of the precious metal of the precious metal precursor. The converting of the first catalyst further comprises preparing a second mixture comprising the first catalyst and the precious metal precursor, and heat-treating the second mixture. The second mixture is heat-treated at 80-400 degrees C for 1-4 hours. EXAMPLE - Palladium-copper catalyst (0.7 g) was added to a mixture of water and isopropyl alcohol (40 g), and dispersed using ultrasonic waves to prepare a mixture. The mixture was added to iridium chloride acid (aqueous) solution (7.237 g) and was reacted at 90 degrees C for 2 hours. The resulting product was filtered, washed, and dried to obtain electrode catalyst.