Selective catalytic reduction (SCR) of NOx at 323-423 K, which is at a relatively lower temperature than that in conventional SCR method using V2O5/TiO2-anatase catalyst, was studied. Catalytic components investigated were transition-metal oxides supported on pitch-based active carbon fibers (ACF). Three transition-metal oxides, Fe2O3, Co2O3 and Mn2O3 were tested as catalytic components, and as a result, Mn2O3 showed the best activity among these metal oxides. As a support material, ACF showed the highest effect among three support materials, including granular active carbons (GAC), and gamma-Al2O3. The activity of Mn2O3/ACF catalyst increased in proportion to the reaction temperature, and NO conversion reached 92% at 423 K. ACF contribute to make highly dispersed metal-oxides particles and large gas-contact surface area.