In order to figure out the catalytic property of hollandite-type hydrous manganese oxide (H-Hol) to remove NH3, the desorption and decomposition properties of NH3 from NH3-chemically adsorbed H-Hol were examined and these properties and NH3 adsorptivity were compared with those of other manganese oxides and a de-NO, catalyst. It was found that the presence of NO accelerates the oxidation of NH3 to form N-2 at a lower temperature. Comparison of NH3 pulse reaction in a flow containing NO on H-Hol with those on a high surface area-manganese oxide and a commercial de-NO, catalyst shows that H-Hol has the greatest N-2 production, but less selectivity to form N-2. H-Hol has a comparable amount of the strong H+ sites with the high surface area manganese oxide, which have relationship with NH3 decomposition.