The present invention relates to a selective oxidation catalyst of ammonia presenting a catalyst range which is manufactured according to the content of active metal and titania carrier when the selective oxidation catalyst of ammonia is manufactured by confirming performance difference according to the physical properties of the titania carrier used as a supporter and a non-precious metal catalyst capable of oxidizing ammonia discharged from denitrification facilities installed in a coal-fired power plant, a fertilizer manufacturing process, an oil refinery, a waste water disposal facility, a vehicle and various industrial facilities into harmless nitrogen. In the present invention, provided is the selective oxidation catalyst of ammonia for oxidizing ammonia into nitrogen, wherein the catalyst finally manufactured according to the content of active metal and titania carrier with a specific surface area (BET) of 43.3 m^2/g or more, a cubic crystallite size of 246 Å or less and an average pore diameter of 24.4 nm or less has a surface density of 1.2-4.5 CeO_x/nm^2, a cubic crystallite size of 37.0-71.0 Å and an average pore diameter of 8.5-11.2 nm, and a method of improving the selective oxidation efficiency of ammonia by using the same.