A metal nitride is provided to harden a surface of steel and obtain abrasion resistance and corrosion resistance by increasing hardness and tensile strength of the metal through salt nitriding. A metal nitride is nitrided in a salt bath having at least one of KNO3, KNO2, Ca(NO3)2, NaN03, and NaNo2 in which a base is a non-cyanogen molten salt. The base is carbon steel or IF steel. The metal nitride has a nitride layer which is formed by nitride diffusion. A compound layer having iron and nitrogen is not contacted in the surface of the metal nitride.
