TECHNOLOGY FOCUS - INORGANIC CHEMISTRY - Preferred Composition: The palladium salt is chosen from palladium chloride, sodium tetrachloro palladate, potassium tetrachloro palladate, ammonium tetrachloro palladate, palladium acetate, palladium oxalate, palladium nitrate, palladium sulfate, palladium acetylacetonate, tetra-amine palladium salt and dinitro diamine palladium salt, preferably sodium tetrachloro palladate. In the palladium core platinum shell nanoparticle colloid, 90% or more of the core particles are single crystals, and 90% or more shell layer comprises five or less layers. More than one half of the surface area of core particles is covered in the shell layer of the platinum atom of mono layer. The shell layer of the palladium core platinum shell nanoparticles covers 50% or more core layer. The platinum atomic layer which comprises the shell exists in the arrangement of the palladium atom on the surface of substrate. The covering state of the platinum atomic layer which comprises the shell is easily analyzed. The platinum raw material salt and the hydroxide ion are mixed with the palladium core nanoparticles combination product. Preferred Process: Manufacture of palladium core platinum shell nanoparticles involves irradiating microwave to the reaction liquid (A) by circulating the reaction liquid (A) in the reaction tube positioned in microwave cavity in microwave exposure. The pH of the reaction liquid (C) is 12, and the reaction liquid (C) is reductively reacted. The palladium core nanoparticle synthesis is performed in continuous flow system. In the microwave exposure process, the reaction tube of continuous flow system is positioned in the biggest position of the standing wave of electric field using microwave resonance cavity and the reaction control of the reaction liquid (A) is performed without impairing the single mode heating method and the rapid heating which irradiates microwave which corresponded to the resonant frequency of the cavity, and microwave uniformity. The surface vicinity uses palladium core particle which is single crystal as core nanoparticles. The surface of palladium core nanoparticles combination product is not contaminated, and platinum raw material salt and hydroxide ion are mixed. The reaction route includes reductive reaction and precipitation reaction of platinum ion which start only in the palladium atom of the palladium particle surface. During manufacture of palladium core platinum shell nanoparticles, the lamination growth of the platinum atomic layer in which palladium core particle is single crystal follows the reductive reaction of platinum ion other than the main reaction route, and precipitation reaction, and in the surface state little unevenness is suppressed. Formation of the palladium core platinum shell nanoparticles is performed using reduction process when the pH of the reaction liquid is 11-13. The palladium core nanoparticles are deposited on the catalyst support such as carbon material and ceramics.