A method of stress inducing transformation from the austenite phase to the martensite phase by conducting cold working on material of austenite stainless steel in the temperature range from the point Ms to the point Md. The above cold working is a biaxial tensing. An intermediately formed hollow body is made, which includes a ferromagnetic portion and a non-magnetic portion contracting inward. Then, the intermediately formed body is subjected to a stress removing process in which residual tensile stress is removed from an intermediately formed body. In the stress removing process, it is preferable that a punch is press-fitted into the intermediately formed body so as to expand a non-magnetic portion and then the intermediately formed body is drawn with ironing while the punch is inserted so that the residual tensile stress can be changed into the residual compressive stress in the non-magnetic portion.