PROBLEM TO BE SOLVED: To provide a weld joint which recovers corrosion resistance on a region heated to a high temperature such as the maximum arrival temperature of about 1100°C or more in a welding heat affected zone formed by welding duplex stainless steel and has superior corrosion resistance in a corrosion environment.SOLUTION: A method for improving corrosion resistance of a duplex stainless steel welded part is characterized in that a cylindrical rotation member is rotated in the range of rotation speed of 100 to 400 rpm while vertically pressing the rotation member along a melting boundary line of a welding joint of duplex stainless steel which contains, by mass% as chemical composition, 20% or more of Cr and 0.1% or more of N and has a micro structure comprising two phases of ferrite and austenite, with a pressing load of 0.5 to 2 ton, and performs heat treatment with frictional heat.
