PURPOSE: To easily produce a steel material for the reduction of NOx having a satisfactory NOx reducing function and superior wear resistance by reducing oxide scale formed on the surface of a steel material and forming the layer of fine metal particles on the surface of the scale by the reduction.

CONSTITUTION: A metallic element such as Ti or V is allowed to penetrate by diffusion into the surface of an iron-based material such as carbon steel or low-alloy steel and this material is formed into a tube or rod shape and used as a base material 1. Since a layer 2 of oxide scale based on Fe2O3 and Fe3O4 is formed on the surface of the base material 1, the surface of the layer 2 is reduced by a method such as heating in the air or in steam to form a layer 3 of fine metal particles. The resulting steel material has satisfactory NOx reducing function and superior wear resistance.