PURPOSE: To improve flexibility and improve a cross-section shape by constituting a reinforcing wire with a piano wire, a stainless wire or a low-carbon two- phase organization steel wire, and forming an Ni-plated film layer on its outer surface.

CONSTITUTION: An Ni-plated film layer 9 is formed on each extra fine wire 5 constituting a reinforcing layer 3, the activity of the extra fine wire 5 itself is decreased, machining distortion is applied to the Ni-plated film layer 9, and the adhesion and adhesive property between synthetic resin 6 and the extra fine wire 5 can be sharply improved. When a low carbon two-phase organization steel wire is used for the extra fine wire 5, a extra fine tube 1 with the outer diameter 0.3-3mm having the reinforcing layer 3 with the wire diameter 10-100μm and very high tensile strength 300-600kgf/mm2 can be obtained. Activity is suppressed and a burnout can be prevented when the extra fine wire 5 with the wire diameter 160μm or below is used, workability can be improved for winding machining, and adhesion and adhesive property can be improved when resin is coated.