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PROBLEM TO BE SOLVED : To provide an underwater use type rare earth-base permanent magnet which exhibits excellent corrosion resistance even when used by being immersed in an oxidative electrolyte solution (etchant) having high corrosiveness, and a method for manufacturing the same. SOLUTION : The permanent magnet is constituted by forming an Ni plating film having characteristics of >=-0.1 V in natural electrode potential (to an SCE saturated calomel electrode) in an aqueous solution containing 10 ppm Cu ions and >=0 V in an aqueous solution containing 100 ppm Cu ions on the extreme surface layer of the magnet surface.