According to the present invention, the catalyst performance of a chelate catalyst comprising a complex of a macrocyclic compound such as a porphyrin derivative is improved. Also, the following method is provided: a method for preparing a fuel cell electrode catalyst comprising a nitrogen-containing metal complex in which a metallic element is coordinated with a macrocyclic organic compound, such method comprising the steps of: adding tin oxalate to the nitrogen-containing metal complex; and baking a mixture of the nitrogen-containing metal complex and tin oxalate in an inert gas atmosphere, wherein elution of metal tin is carried out via acid treatment.