An electric wire with terminal connector including an electric wire having a core wire including a plurality of wires and a female terminal connector including a wire barrel that is crimped onto the core wire exposed from the electric wire, the following steps are executed. The steps include a step of removing wire insulation covering an outer peripheral surface of the core wire to expose the core wire, a step of holding the exposed core wire with jigs provided in a pair and applying ultrasonic vibration to the core wire via the jigs, and a step of crimping the wire barrel so as to surround a part of the core wire to which the ultrasonic vibration is applied.