NOVELTY - An oxidation catalyst comprises one or more transition element chosen from platinum, palladium and rhodium, and is supported on a carrier. The radius of pores in the oxidation catalyst is 2-100 nm. The ratio of surface area formed by pore having radius of 10 nm or more is 49% or more, with respect to total surface area of pores of the oxidation catalyst.    USE - Oxidation catalyst is used in waste gas processing apparatus for oxidation of flammable component and removal of nitrogen oxide (all claimed).    ADVANTAGE - The oxidation catalyst enables efficient and environmentally-friendly oxidation of flammable component, with reduced content of active metal groups, at higher space velocity and low temperature.    DETAILED DESCRIPTION - INDEPENDENT CLAIMS are included for the following:    (1) waste gas processing apparatus, which comprises combustion catalyst portion which burns the non-combusted component contained in to-be-processed gas using catalyst, and in which the combustion catalyst portion is filled with the oxidation catalyst;    (2) thermal storage combustion burner, which comprises a air-fuel mixture injection portion which injects a fuel and the air-fuel mixture of a combustion air, thermal storage portion which heats the combustion air by calorie amount by which to-be-processed gas is distributed, and the sensible heat is thermally stored to the thermal storage component, and the combustion air is distributed after thermal storage, and combustion catalyst portion provided between the thermal storage portion and the air-fuel mixture injection portion or the thermal storage portion, filled with the oxidation catalyst;    (3) oxidation of flammable component in gas, which involves oxidizing flammable component chosen from water vapor and carbon monoxide in to-be-processed gas containing sulfur oxide, nitrogen monoxide, and methane, using the oxidation catalyst; and    (4) removal of nitrogen oxide in gas, which involves positioning the combustion catalyst portion between the gas heating portion and the denitration portion, heating the to-be-processed gas by passing through the gas heating portion, burning the flammable component in the to-be-processed gas, raising the temperature of the to-be-processed gas with the combustion heat, and removing the nitrogen oxide in to-be-processed gas.