A used denitration catalyst is regenerated by means of a method comprising bringing the used denitration catalyst comprising titanium oxide as an essential ingredient into contact with a suspension of particles comprising manganese oxide, subjecting the resulting product to a liquid draining, and subjecting the liquid-drained product to a drying process, additionally, further comprising impregnating a solution comprising a compound containing at least one element selected from the group consisting of vanadium, molybdenum and tungsten into the denitration catalyst after the drying process, and subjecting the impregnated product to a drying treatment.