This invention provides a method for high efficiency, high concentration production of hydrogen peroxide wherein oxygen and hydrogen are reacted in the reaction medium in the presence of a catalyst comprising a metallic or carrier supported platinum group metal catalyst onto which an organic halogen compound which is insoluble in water, which compound excludes compounds which contain no halogen other than fluorine, has been adsorbed or a platinum group metal catalyst supported on a carrier in which a halogenated organic compound, which compound excludes compounds that contain no halogen other than fluorine, has been adsorbed to the carrier prior to supporting the platinum group metal. Since it is not necessary for halogen ions to be present in the reaction medium as it was in the prior art, the problems of deterioration due to the dissolution of the catalyst and of corrosion of the structural materials of the reaction vessel are alleviated.