In a method of making a metallic thin wire 1, one single metallic thin wire 2 is prepared to have a predetermined length with a middle portion of the one single metallic thin wire 2 as a fixed portion. Front and rear half portions of the one single metallic thin wire 2 are twisted with a tensile weight W applied to the front and rear half portions in the lengthwise direction. The one single metallic thin wire 2 is processed with a heat treatment to remove a residual stress. This provides the metallic thin wire 1 with a high rotation-following capability and high torque transmissibility, thus enabling artisans to usefully apply the metallic thin wire 1 to a main wire component 25 of a medical tool and equipment.