NOVELTY - An aqueous solution of transition metal compound is contacted with ammonia and/or aqueous ammonia and deposit (A) containing atom of transition metal is produced. Deposit (A), an organic compound, and a liquid medium are mixed to obtain a catalyst precursor. The catalyst precursor is heat-processed at 500-1200 degrees C to obtain an electrode catalyst. A portion of or all transition metal compound contains transition metal element chosen from group 4 element and group 5 element.    USE - Manufacture of electrode catalyst for forming layers of electrodes in manufacture of fuel cells e.g. polymer electrolyte fuel cells (all claimed). Uses include but are not limited to fluorescent lamps, signal apparatus, motor vehicles, domestic electrical appliances, agricultural apparatus, mobile telephones, portable tools, furniture, toys, bulletin boards, cardiac pacemakers, and outdoor generators.    ADVANTAGE - The method enables manufacture of electrode catalyst having excellent catalytic activity and workability, by heat-treatment at low temperature. The catalyst provides electrodes having excellent durability and corrosion resistance.    DETAILED DESCRIPTION - An aqueous solution of transition metal compound is contacted with ammonia and/or aqueous ammonia and deposit (A) containing atom of transition metal is produced. Deposit (A), an organic compound, and a liquid medium are mixed to obtain a catalyst precursor. The catalyst precursor is heat-processed at 500-1200 degrees C to obtain an electrode catalyst. A portion of or all transition metal compound contains transition metal element chosen from group 4 element and group 5 element. The organic compound is sugar, aminosugar, glucosaminoglycan, polyvinyl alcohol, polyalkylene glycol, polyester, nitrogen-containing high-molecular compound, nitrile-group-containing compound, amino acid, and/or organic acid. INDEPENDENT CLAIMS are included for the following:    (1) manufacture of electrode catalyst layer;    (2) manufacture of electrode;    (3) manufacture of membrane electrode assembly; and    (4) manufacture of fuel cell.