A reinforced member which is made from a steel product having a strain aging characteristic and has a closed section at a cross section perpendicular to an axis of the reinforced member. The reinforced member includes a reinforced area which is produced by press-forming the steel product so as to generate a compression strain in the press-formed steel product due to the application of a compression stress to the steel product along the direction from a surface of the steel product to an inside of the steel product, and by giving a strain aging treatment to the press-formed member.