A nitriding treatment method of a steel member, in which a nitriding treatment step is performed in which the steel member is subjected to a nitriding treatment in a nitriding gas atmosphere having a nitriding potential with which a γ′ phase or ε phase iron nitride compound layer is generated on a surface of the steel member, and then, a passing step is performed in which the steel member is made to pass through an atmosphere at 425° C. to 600° C. where the iron nitride compound layer does not grow over five minutes or more, the iron nitride compound layer has the γ′ phase uppermost surface layer, and the γ′ phase is made to precipitate in the iron nitride compound layer by the proportion of 40% or more.