A PC strand is untwisted to separate surrounding wires from a core wire, a synthetic resin powdered coating material is uniformly adhered by being applied and heated over the outer periphery of the core wire and surrounding wires in this untwisted state, the product is cooled to form a resin film, and then the surrounding wires are twisted back to the original state with respect to the core wire. Pre-heating is performed before the coating step and post-heating is performed after the coating step, the pre-heating temperature is set 30 to 130° C. higher than the post-heating temperature, a synthetic resin powdered coating material having an average grain size of 40 to 50 μm is used, and the process line speed is 5 to 10 m/min.