NOVELTY - A powder material (11) contains nanoparticles (14) having core-shell structure, and microparticles (15) containing conductive carbon. The core portion (12) contains platinum. The shell portion (13) formed on the core portion contains metal oxide of trivalent or tetravalent cerium or zirconium. The molar ratio of metal oxide and platinum is 0.001-0.2. The molar ratio of metal oxide and conductive carbon is 0.0001-0.15. The metal oxide is amorphous substance. Portion of amorphous substance is crystalline. 80 Volume% or more of trivalent cation is contained in the powder material.    USE - Powder material is used for electrode for polymeric fuel cell (claimed) used as power supply for motor vehicle and household appliances, and sensor.    ADVANTAGE - The powder material has excellent oxygen-reductive decomposition activity, and reduced carbon monoxide poisoning.    DETAILED DESCRIPTION - A powder material contains nanoparticle having core-shell structure, and microparticles containing conductive carbon. The core portion contains platinum. The shell portion formed on the core portion contains metal oxide of trivalent or tetravalent cerium or zirconium. The molar ratio of metal oxide and platinum is 0.001-0.2. The molar ratio of metal oxide and conductive carbon is 0.0001-0.15. The metal oxide is amorphous substance. Portion of amorphous substance is crystalline. 80 Volume% or more of trivalent cation is contained in the powder material. The compositional formula of powder material is XxPt/Yx metal oxide/Zx conductive carbon, where X,Y and Z are composition of metal oxide, platinum and conductive carbon. INDEPENDENT CLAIMS are included for the following:    (1) manufacture of powder material, which involves adding solution containing metal ion of cerium or zirconium in ammonium carbonate aqueous solution or ammonium hydrogen carbonate aqueous solution, obtaining solution (A) having precipitated metal oxide powder, drying, calcining in chloroplatinic acid aqueous solution, drying baking, forming platinum-containing metal oxide powder, adding predetermined amount of conductive carbon, applying oxidation-reduction potential and forming powder material; and    (2) polymeric fuel cell, which has base material containing solid polymer electrolyte, primary electrode formed on one surface of the base material, secondary electrode formed on other surface. The primary electrode and secondary electrode contain powder material.    DESCRIPTION OF DRAWING(S) - The drawing shows a schematic view explaining manufacture of powder material.    Powder material (11)    Core portion (12)    Shell portion (13)    Nanoparticles (14)    Microparticles (15)