PURPOSE: To enhance denitration rate and eliminate generation of harmful gas by immersing a carbonaceous substance treated with sulfuric acid and having a specific surface area value in iron salt solution, also immersing the same in wet state into aq. alkali solution and then calcing.

CONSTITUTION: A carbonaceous substance with specific surface area of 30W1,500m2/g is treated with sulfuric acid or sulfate to manufacture sulfuric acid treated carbon material. Surplus liquid is separated after said sulfuric acid treated carbon material is immersed in iron salt solution, and then the carbon material permeated sufficiently with iron salt solution in the wet state is immersed in alkali water solution. By said process, iron salt on the carbon material or in pores is converted into iron hydroxide and then separated, washed and dried, and if necessary, calcined to manufacture catalysts for denitration. As for the iron salt to be used, chloride, nitrate, etc., is suitable, and the water solution of 500ppm or more is suitable for use.